security: internal audit — batch 1

Fixes the critical + high + medium findings from our internal security
review. Bundled into one PR because the changes overlap heavily (JWT
verification unifies across three call sites; backup-code hashing and
demo-email handling cross-cut several services); splitting them out
would mean redundant reviews of the same files.

Critical
- CI-C1 — .github/workflows/test.yml: restore actions/{checkout,setup-
  node,upload-artifact} to @v4. The @v6 refs don't exist, so the test
  workflow was errorring before a single test ran.
- SEC-C1 — mfaPolicy now extracts the token via extractToken() (cookie-
  first, Bearer fallback). Previously it only read Authorization, so
  every cookie-authenticated SPA session bypassed require_mfa entirely.
- SEC-C2/C4/C6 — all JWT verification paths (MCP bearer, file download,
  photo route) now go through the shared verifyJwtAndLoadUser that
  checks password_version. resetPassword additionally deletes every
  mcp_tokens row and marks outstanding oauth_tokens revoked, so a
  password reset invalidates ALL credential classes — not just the
  cookie JWT.

High
- SEC-H2 — reset email URL is built from server-side APP_URL /
  ALLOWED_ORIGINS (via existing getAppUrl()), not request headers.
  Closes the host-header-injection vector into reset links.
- SEC-H3 — OIDC findOrCreateUser wraps the invite-redemption UPDATE +
  user INSERT in a transaction. The UPDATE is the capacity check; if
  a concurrent callback takes the last slot, the whole transaction
  aborts with registration_disabled instead of double-creating users.
- SEC-H4 — new verifyIdToken() performs full JWT signature
  verification via the provider's JWKS (Node's crypto.createPublicKey
  accepts JWK directly — no extra dependency), plus iss/aud/exp
  checks. The callback also rejects the login when userinfo.sub does
  not match id_token.sub.
- SEC-H5 — OAuth DCR now validates redirect_uris against an allowlist
  of schemes: https, http-loopback, or a private custom scheme. Plain
  http://non-loopback is rejected.
- SEC-H6 — oauthService audience defaults to mcpResource when the
  `resource` parameter is missing, so tokens are always audience-bound
  to /mcp instead of being issued with audience=null.
- SEC-H7 — HSTS is enabled any time NODE_ENV=production (previously
  required FORCE_HTTPS=true), includeSubDomains defaults on and can
  be disabled with HSTS_INCLUDE_SUBDOMAINS=false.
- SEC-H8 — trek_session cookie Secure flag is also driven by
  req.secure (which Express resolves from X-Forwarded-Proto once
  trust proxy is set), so instances behind a TLS-terminating proxy
  get Secure cookies without needing FORCE_HTTPS.

Medium
- SEC-M1 — permanentDeleteFile / emptyTrash / avatar unlink now use
  fs.promises.rm with { force: true } (one async op vs the previous
  existsSync + unlinkSync pair per file).
- SEC-M2 — invalidatePermissionsCache() is called inside restoreFromZip
  so a restored DB with different permission rows is honoured
  immediately.
- SEC-M3 + C1 — idempotency store bounds the key at 128 chars, caches
  only responses ≤ 256 KiB, and scopes the lookup by (key, user_id,
  method, path) rather than (key, user_id). Same key replayed against
  a different endpoint no longer returns a stale unrelated body.
- SEC-M4 — share_tokens gets an expires_at column; new tokens default
  to 90-day TTL, expired tokens are denied at lookup. Existing tokens
  stay NULL = no expiry so already-published links don't break.
- SEC-M5 — /uploads/photos/:filename now resolves the photo to its
  trip_id and requires the share token to cover THAT trip. Previously
  any share token for any trip would unlock any photo filename.
- SEC-M6 — BLOCKED_EXTENSIONS is the single source of truth shared
  between fileService and collab uploads. The '*' allowed_file_types
  wildcard now still rejects executables/scripts.
- SEC-M7 — single DEMO_EMAILS constant (services/demo.ts) used by
  demoUploadBlock, mfaPolicy, and every demo-mode guard in
  authService. The old demoUploadBlock only matched 'demo@nomad.app'
  so the seed 'demo@trek.app' could in fact upload in demo mode.
- SEC-M8 — MFA backup codes are now bcrypt-hashed at rest
  (hashBackupCodeBcrypt). matchBackupCode accepts both bcrypt and
  legacy SHA-256 hex hashes, so existing installs keep working until
  the user regenerates codes via enableMfa.
- SEC-M9 — document the "security via UUID v4 filename" model for
  /uploads/avatars|covers|journey. Requires no code change but
  captures the decision so future reviewers don't re-flag it.
- SEC-M10 — already covered by the resetPassword revocation logic
  above: mcp_tokens DELETE + oauth_tokens UPDATE … SET revoked_at.

Performance
- PERF-H1 — new migration adds the indexes flagged in the audit:
  trips(user_id), trips(created_at DESC), photos(day_id),
  photos(place_id), reservations(day_id), share_tokens(token), plus
  conditional day_accommodations and notifications indexes depending
  on which columns are present.

Tests
- tests/integration/oidc.test.ts now mocks verifyIdToken and passes
  an id_token in the exchangeCodeForToken stub for the three flows
  that exercise a successful callback. The three remaining failures
  tests pointed out were all pre-existing (file-upload flakes +
  notificationPreferences event_types count drift), none introduced
  by this PR.

server/src/services/shareService.ts

@@ -44,9 +44,14 @@ export function createOrUpdateShareLink(
     return { token: existing.token, created: false };
   }
 
+  // New share links default to a 90-day TTL. Existing tokens that were
+  // created before the expires_at migration keep NULL here and remain
+  // valid indefinitely until the owner rotates them; that preserves
+  // behaviour for anyone who's already sharing a link.
   const token = crypto.randomBytes(24).toString('base64url');
-  db.prepare('INSERT INTO share_tokens (trip_id, token, created_by, share_map, share_bookings, share_packing, share_budget, share_collab) VALUES (?, ?, ?, ?, ?, ?, ?, ?)')
-    .run(tripId, token, createdBy, share_map ? 1 : 0, share_bookings ? 1 : 0, share_packing ? 1 : 0, share_budget ? 1 : 0, share_collab ? 1 : 0);
+  const expiresAt = new Date(Date.now() + 90 * 24 * 60 * 60 * 1000).toISOString();
+  db.prepare('INSERT INTO share_tokens (trip_id, token, created_by, share_map, share_bookings, share_packing, share_budget, share_collab, expires_at) VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?)')
+    .run(tripId, token, createdBy, share_map ? 1 : 0, share_bookings ? 1 : 0, share_packing ? 1 : 0, share_budget ? 1 : 0, share_collab ? 1 : 0, expiresAt);
   return { token, created: true };
 }
 
@@ -79,7 +84,9 @@ export function deleteShareLink(tripId: string): void {
  * permission flags. Returns null if the token is invalid or the trip is gone.
  */
 export function getSharedTripData(token: string): Record<string, any> | null {
-  const shareRow = db.prepare('SELECT * FROM share_tokens WHERE token = ?').get(token) as any;
+  const shareRow = db.prepare(
+    "SELECT * FROM share_tokens WHERE token = ? AND (expires_at IS NULL OR expires_at > datetime('now'))"
+  ).get(token) as any;
   if (!shareRow) return null;
 
   const tripId = shareRow.trip_id;