feat(costs): rework Budget into Costs — Splitwise-style, multi-currency, mobile (#1106)

* fix(journey): authorize reads of the journey share link

GET /api/journeys/:id/share-link now requires journey access (canAccessJourney),
matching the create/delete share-link routes and the get_journey_share_link MCP
tool. Returns no link when the caller lacks access to the journey.

* feat(costs): rework Budget into Costs — Splitwise-style, multi-currency, mobile

Renames the Budget addon to "Costs" (UI only) and reworks it into a Tricount/
Splitwise-style cost tracker: multiple payers per expense, equal split across
chosen members, settle-up with persisted history + undo, 12 fixed categories,
per-expense currency with live FX conversion to a user-set display currency
(Settings -> Display), and locale-correct money formatting. Adds a desktop and a
dedicated mobile layout. A migration backfills existing budget items (single
payer, split members, currency). Closes #551 (per-expense currency).

Also switches the app font to self-hosted Poppins (Geist for secondary subtext),
replacing the Google Fonts CDN dependency.

* fix(costs): neutral dashboard dark palette + liquid glass, full page width, entry-count badge

- Dark mode used a warm oklch palette that read brownish; switch to the
  neutral zinc tokens used by the dashboard (#121215 bg, #f4f4f5 ink) and add a
  subtle backdrop-blur glass on cards.
- Costs now uses the full available page width on desktop instead of a 1280px cap.
- Render the expense count next to the Expenses title as a badge.
- Adapt budget/journey unit tests to the new payer-based settlement model and the
  Costs rename (category default 'other', Costs tab/CostsPanel).

* fix(costs): drop the entry-count badge, always show row edit/delete actions

Removes the count badge next to the Expenses title and makes the per-row
edit/delete actions permanently visible (no longer hover-only) on desktop too.

* feat(costs): currency-native money formatting, custom select/date, rename addon to Costs

- Format every amount in its own currency convention (symbol position, grouping
  and decimal separators) regardless of app language, via a currency->locale map
  (EUR -> '12,00 €', USD -> '$12.00', JPY -> '¥12', ...). Previously Intl used the
  app locale, so EUR showed the symbol in front under an English UI.
- Use TREK's CustomSelect (searchable, with symbols) and CustomDatePicker in the
  add/edit expense modal instead of the native <select>/<input type=date>.
- Rename the 'Budget Planner' add-on to 'Costs' in the admin list (display only;
  id/tables/permissions/MCP stay 'budget') via seed + a migration for existing DBs.

* feat(auth): configurable session duration via SESSION_DURATION

Adds a SESSION_DURATION env var (ms-style strings: 1h, 7d, 30d, ...) controlling
how long a session stays valid before re-login. It drives both the trek_session
JWT exp claim and the cookie maxAge from one source, so they never drift. Invalid
values warn at startup and fall back to the default (24h — unchanged). The MFA
challenge token and MCP OAuth tokens keep their own TTL.

Implements the request from discussion #946. Documented in the env-var wiki page,
.env.example and docker-compose.yml.

server/tests/unit/services/budgetService.test.ts

@@ -2,26 +2,14 @@ import { describe, it, expect, vi, beforeEach } from 'vitest';
 
 // ── DB mock setup ────────────────────────────────────────────────────────────
 
-interface MockPrepared {
-  all: ReturnType<typeof vi.fn>;
-  get: ReturnType<typeof vi.fn>;
-  run: ReturnType<typeof vi.fn>;
-}
-
-const preparedMap: Record<string, MockPrepared> = {};
-let defaultAll: ReturnType<typeof vi.fn>;
-let defaultGet: ReturnType<typeof vi.fn>;
-
 const mockDb = vi.hoisted(() => {
   return {
     db: {
-      prepare: vi.fn((sql: string) => {
-        return {
-          all: vi.fn(() => []),
-          get: vi.fn(() => undefined),
-          run: vi.fn(),
-        };
-      }),
+      prepare: vi.fn(() => ({
+        all: vi.fn(() => []),
+        get: vi.fn(() => undefined),
+        run: vi.fn(),
+      })),
     },
     canAccessTrip: vi.fn(() => true),
   };
@@ -30,25 +18,29 @@ const mockDb = vi.hoisted(() => {
 vi.mock('../../../src/db/database', () => mockDb);
 
 import { calculateSettlement } from '../../../src/services/budgetService';
-import type { BudgetItem, BudgetItemMember } from '../../../src/types';
+import type { BudgetItem, BudgetItemMember, BudgetItemPayer } from '../../../src/types';
 
 // ── Helpers ──────────────────────────────────────────────────────────────────
+// Who actually paid is recorded as explicit payers (budget_item_payers); members
+// are only the equal-split participants.
 
 function makeItem(id: number, total_price: number, trip_id = 1): BudgetItem {
-  return { id, trip_id, name: `Item ${id}`, total_price, category: 'Other' } as BudgetItem;
+  return { id, trip_id, name: `Item ${id}`, total_price, category: 'other' } as BudgetItem;
 }
 
-function makeMember(budget_item_id: number, user_id: number, paid: boolean | 0 | 1, username: string): BudgetItemMember & { budget_item_id: number } {
-  return {
-    budget_item_id,
-    user_id,
-    paid: paid ? 1 : 0,
-    username,
-    avatar: null,
-  } as BudgetItemMember & { budget_item_id: number };
+function makeMember(budget_item_id: number, user_id: number, username: string): BudgetItemMember & { budget_item_id: number } {
+  return { budget_item_id, user_id, paid: 0, username, avatar: null } as BudgetItemMember & { budget_item_id: number };
 }
 
-function setupDb(items: BudgetItem[], members: (BudgetItemMember & { budget_item_id: number })[]) {
+function makePayer(budget_item_id: number, user_id: number, amount: number, username: string): BudgetItemPayer & { budget_item_id: number } {
+  return { budget_item_id, user_id, amount, username, avatar: null } as BudgetItemPayer & { budget_item_id: number };
+}
+
+function setupDb(
+  items: BudgetItem[],
+  members: (BudgetItemMember & { budget_item_id: number })[],
+  payers: (BudgetItemPayer & { budget_item_id: number })[] = [],
+) {
   mockDb.db.prepare.mockImplementation((sql: string) => {
     if (sql.includes('SELECT * FROM budget_items')) {
       return { all: vi.fn(() => items), get: vi.fn(), run: vi.fn() };
@@ -56,45 +48,51 @@ function setupDb(items: BudgetItem[], members: (BudgetItemMember & { budget_item
     if (sql.includes('budget_item_members')) {
       return { all: vi.fn(() => members), get: vi.fn(), run: vi.fn() };
     }
+    if (sql.includes('budget_item_payers')) {
+      return { all: vi.fn(() => payers), get: vi.fn(), run: vi.fn() };
+    }
+    // budget_settlements and anything else → empty
     return { all: vi.fn(() => []), get: vi.fn(), run: vi.fn() };
   });
 }
 
 beforeEach(() => {
   vi.clearAllMocks();
-  setupDb([], []);
+  setupDb([], [], []);
 });
 
 // ── calculateSettlement ──────────────────────────────────────────────────────
 
 describe('calculateSettlement', () => {
   it('returns empty balances and flows when trip has no items', () => {
-    setupDb([], []);
+    setupDb([], [], []);
     const result = calculateSettlement(1);
     expect(result.balances).toEqual([]);
     expect(result.flows).toEqual([]);
   });
 
   it('returns no flows when there are items but no members', () => {
-    setupDb([makeItem(1, 100)], []);
+    setupDb([makeItem(1, 100)], [], [makePayer(1, 1, 100, 'alice')]);
     const result = calculateSettlement(1);
     expect(result.flows).toEqual([]);
   });
 
-  it('returns no flows when no one is marked as paid', () => {
+  it('returns no flows when no one has paid', () => {
     setupDb(
       [makeItem(1, 100)],
-      [makeMember(1, 1, 0, 'alice'), makeMember(1, 2, 0, 'bob')],
+      [makeMember(1, 1, 'alice'), makeMember(1, 2, 'bob')],
+      [],
     );
     const result = calculateSettlement(1);
     expect(result.flows).toEqual([]);
   });
 
   it('2 members, 1 payer: payer is owed half, non-payer owes half', () => {
-    // Item: $100. Alice paid, Bob did not. Each owes $50. Alice net: +$50. Bob net: -$50.
+    // Item: $100. Alice paid all, [Alice, Bob] split. Each owes $50. Alice net: +$50. Bob: -$50.
     setupDb(
       [makeItem(1, 100)],
-      [makeMember(1, 1, 1, 'alice'), makeMember(1, 2, 0, 'bob')],
+      [makeMember(1, 1, 'alice'), makeMember(1, 2, 'bob')],
+      [makePayer(1, 1, 100, 'alice')],
     );
     const result = calculateSettlement(1);
     const alice = result.balances.find(b => b.user_id === 1)!;
@@ -111,7 +109,8 @@ describe('calculateSettlement', () => {
     // Item: $90. Alice paid. Each of 3 owes $30. Alice net: +$60. Bob: -$30. Carol: -$30.
     setupDb(
       [makeItem(1, 90)],
-      [makeMember(1, 1, 1, 'alice'), makeMember(1, 2, 0, 'bob'), makeMember(1, 3, 0, 'carol')],
+      [makeMember(1, 1, 'alice'), makeMember(1, 2, 'bob'), makeMember(1, 3, 'carol')],
+      [makePayer(1, 1, 90, 'alice')],
     );
     const result = calculateSettlement(1);
     const alice = result.balances.find(b => b.user_id === 1)!;
@@ -124,12 +123,11 @@ describe('calculateSettlement', () => {
   });
 
   it('all paid equally: all balances are zero, no flows', () => {
-    // Item: $60. 3 members, all paid equally (each paid $20, each owes $20). Net: 0.
-    // Actually with "paid" flag it means: paidPerPayer = item.total / numPayers.
-    // If all 3 paid: each gets +20 credit, each owes -20 = net 0 for everyone.
+    // Item: $60. 3 members, each paid $20 and owes $20. Net: 0 for everyone.
     setupDb(
       [makeItem(1, 60)],
-      [makeMember(1, 1, 1, 'alice'), makeMember(1, 2, 1, 'bob'), makeMember(1, 3, 1, 'carol')],
+      [makeMember(1, 1, 'alice'), makeMember(1, 2, 'bob'), makeMember(1, 3, 'carol')],
+      [makePayer(1, 1, 20, 'alice'), makePayer(1, 2, 20, 'bob'), makePayer(1, 3, 20, 'carol')],
     );
     const result = calculateSettlement(1);
     for (const b of result.balances) {
@@ -142,7 +140,8 @@ describe('calculateSettlement', () => {
     // Alice paid $100 for 2 people. Bob owes Alice $50.
     setupDb(
       [makeItem(1, 100)],
-      [makeMember(1, 1, 1, 'alice'), makeMember(1, 2, 0, 'bob')],
+      [makeMember(1, 1, 'alice'), makeMember(1, 2, 'bob')],
+      [makePayer(1, 1, 100, 'alice')],
     );
     const result = calculateSettlement(1);
     const flow = result.flows[0];
@@ -154,7 +153,8 @@ describe('calculateSettlement', () => {
     // Item: $10. 3 members, 1 payer. Share = 3.333... Each rounded to 3.33.
     setupDb(
       [makeItem(1, 10)],
-      [makeMember(1, 1, 1, 'alice'), makeMember(1, 2, 0, 'bob'), makeMember(1, 3, 0, 'carol')],
+      [makeMember(1, 1, 'alice'), makeMember(1, 2, 'bob'), makeMember(1, 3, 'carol')],
+      [makePayer(1, 1, 10, 'alice')],
     );
     const result = calculateSettlement(1);
     for (const b of result.balances) {
@@ -176,9 +176,10 @@ describe('calculateSettlement', () => {
     setupDb(
       [makeItem(1, 100), makeItem(2, 60)],
       [
-        makeMember(1, 1, 1, 'alice'), makeMember(1, 2, 0, 'bob'),
-        makeMember(2, 1, 0, 'alice'), makeMember(2, 2, 1, 'bob'),
+        makeMember(1, 1, 'alice'), makeMember(1, 2, 'bob'),
+        makeMember(2, 1, 'alice'), makeMember(2, 2, 'bob'),
       ],
+      [makePayer(1, 1, 100, 'alice'), makePayer(2, 2, 60, 'bob')],
     );
     const result = calculateSettlement(1);
     const alice = result.balances.find(b => b.user_id === 1)!;