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.

shared/src/i18n/gr/budget.ts

@@ -40,5 +40,78 @@ const budget: TranslationStrings = {
     'Κάντε κλικ στο avatar ενός μέλους σε μια εγγραφή προϋπολογισμού για να το επισημάνετε πράσινο — αυτό σημαίνει ότι πλήρωσε. Η εκκαθάριση δείχνει στη συνέχεια ποιος χρωστάει σε ποιον και πόσα.',
   'budget.netBalances': 'Καθαρά Υπόλοιπα',
   'budget.categoriesLabel': 'κατηγορίες',
+  "costs.you": "You",
+  "costs.youShort": "Y",
+  "costs.youLower": "you",
+  "costs.youOwe": "You owe",
+  "costs.youOweSub": "You should pay others",
+  "costs.youreOwed": "You're owed",
+  "costs.youreOwedSub": "Others should pay you",
+  "costs.totalSpend": "Total trip spend",
+  "costs.totalSpendSub": "Across all travelers",
+  "costs.to": "To",
+  "costs.from": "From",
+  "costs.allSettled": "You're all settled up",
+  "costs.nothingOwed": "Nothing owed to you",
+  "costs.yourShare": "Your share",
+  "costs.youPaid": "You paid",
+  "costs.expenses": "Expenses",
+  "costs.entries": "{count} entries",
+  "costs.searchPlaceholder": "Search expenses…",
+  "costs.filter.all": "All",
+  "costs.filter.mine": "Paid by me",
+  "costs.filter.owed": "I'm owed",
+  "costs.addExpense": "Add expense",
+  "costs.editExpense": "Edit expense",
+  "costs.noMatch": "No expenses match your search.",
+  "costs.emptyText": "No expenses yet. Add your first one.",
+  "costs.spent": "{amount} spent",
+  "costs.noDate": "No date",
+  "costs.noOnePaid": "No one paid yet",
+  "costs.youLent": "you lent {amount}",
+  "costs.youBorrowed": "you borrowed {amount}",
+  "costs.settleUp": "Settle up",
+  "costs.history": "History",
+  "costs.everyoneSquare": "Everyone's square",
+  "costs.nothingOutstanding": "No payments outstanding right now.",
+  "costs.pay": "pay",
+  "costs.pays": "pays",
+  "costs.settle": "Settle",
+  "costs.balances": "Balances",
+  "costs.byCategory": "By category",
+  "costs.noCategories": "No expenses yet.",
+  "costs.settleHistory": "Settle history",
+  "costs.noSettlements": "No settled payments yet.",
+  "costs.paymentsSettled": "{count} payments settled",
+  "costs.paid": "paid",
+  "costs.undo": "Undo",
+  "costs.whatFor": "What was it for?",
+  "costs.namePlaceholder": "e.g. Dinner, souvenirs, gas…",
+  "costs.totalAmount": "Total amount",
+  "costs.currency": "Currency",
+  "costs.day": "Day",
+  "costs.rateLabel": "1 {from} in {to}",
+  "costs.category": "Category",
+  "costs.whoPaid": "Who paid?",
+  "costs.splitBetween": "Split equally between",
+  "costs.pickSomeone": "Pick at least one person to split with.",
+  "costs.splitSummary": "Split {count} ways · {amount} each",
+  "costs.cat.accommodation": "Accommodation",
+  "costs.cat.food": "Food & drink",
+  "costs.cat.groceries": "Groceries",
+  "costs.cat.transport": "Transport",
+  "costs.cat.flights": "Flights",
+  "costs.cat.activities": "Activities",
+  "costs.cat.sightseeing": "Sightseeing",
+  "costs.cat.shopping": "Shopping",
+  "costs.cat.fees": "Fees & tickets",
+  "costs.cat.health": "Health",
+  "costs.cat.tips": "Tips",
+  "costs.cat.other": "Other",
+  "costs.daysCount": "{count} days",
+  "costs.travelers": "{count} travelers",
+  "costs.liveRate": "live rate",
+  "costs.settleAll": "Settle all",
 };
+
 export default budget;

shared/src/i18n/gr/settings.ts

@@ -301,5 +301,8 @@ const settings: TranslationStrings = {
   'settings.mfa.toastDisabled':
     'Ο έλεγχος ταυτότητας δύο παραγόντων απενεργοποιήθηκε',
   'settings.mfa.demoBlocked': 'Δεν είναι διαθέσιμο σε λειτουργία demo',
+  "settings.currency": "Currency",
+  "settings.currencyHint": "All amounts in Costs are converted to and shown in this currency.",
 };
+
 export default settings;

shared/src/i18n/gr/trip.ts

@@ -9,7 +9,7 @@ const trip: TranslationStrings = {
   'trip.tabs.packingShort': 'Αποσκευές',
   'trip.tabs.lists': 'Λίστες',
   'trip.tabs.listsShort': 'Λίστες',
-  'trip.tabs.budget': 'Προϋπολογισμός',
+  'trip.tabs.budget': "Costs",
   'trip.tabs.files': 'Αρχεία',
   'trip.loading': 'Φόρτωση ταξιδιού...',
   'trip.loadingPhotos': 'Φόρτωση φωτογραφιών μέρους...',