fix: prevent cold-path hang when Dexie write transactions stall after external IDB clear

When DevTools "Clear site data" deletes the IDB while the tab is open, Dexie
receives a versionchange event and closes its connection. On reopen, read
transactions work (toArray completes after ~400ms), but write transactions can
stall indefinitely, causing the cold-path 'await refresh' to never resolve.

Two changes:
- Make upsertTrip calls fire-and-forget in the IIFE so network data is returned
  immediately without blocking on potentially-stuck IDB writes.
- Add a 2-second timeout to the initial offlineDb.trips.toArray() call so that
  if the read also stalls, the cold path falls through to the network fetch.
- Reduce the outer dashboard timeout from 12s to 5s now that the inner path
  cannot stall for more than ~2s + network RTT.

client/src/pages/DashboardPage.tsx

@@ -744,7 +744,11 @@ export default function DashboardPage(): React.ReactElement {
   const loadTrips = async () => {
     setIsLoading(true)
     try {
-      const { trips, archivedTrips, refresh } = await tripRepo.list()
+      const listOrTimeout = Promise.race([
+        tripRepo.list(),
+        new Promise<never>((_, reject) => setTimeout(() => reject(new Error('trips-load-timeout')), 5_000)),
+      ])
+      const { trips, archivedTrips, refresh } = await listOrTimeout
       setTrips(sortTrips(trips))
       setArchivedTrips(sortTrips(archivedTrips))
       setIsLoading(false)

client/src/repo/tripRepo.ts

@@ -8,7 +8,12 @@ type TripRefresh = Promise<{ trip: Trip } | null>
 
 export const tripRepo = {
   async list(): Promise<{ trips: Trip[]; archivedTrips: Trip[]; refresh: TripsRefresh }> {
-    const all = await offlineDb.trips.toArray()
+    // 2-second guard: if Dexie is in a bad state (e.g. externally deleted while tab
+    // was open), toArray() may hang. Fall back to the cold/network path.
+    const all = await Promise.race([
+      offlineDb.trips.toArray(),
+      new Promise<Trip[]>(resolve => setTimeout(() => resolve([]), 2000)),
+    ])
 
     const refresh: TripsRefresh = (async () => {
       try {
@@ -16,6 +21,8 @@ export const tripRepo = {
           tripsApi.list(),
           tripsApi.list({ archived: 1 }),
         ])
+        // Fire-and-forget IDB writes: returning data immediately unblocks the cold
+        // path even when Dexie write transactions stall after an external DB clear.
         Promise.all([
           ...active.trips.map(t => upsertTrip(t)),
           ...archived.trips.map(t => upsertTrip(t)),
@@ -36,11 +43,6 @@ export const tripRepo = {
 
     const fresh = await refresh
     if (!fresh) return { trips: [], archivedTrips: [], refresh: Promise.resolve(null) }
-    // Await upserts on cold path so next mount reads from IDB instead of hitting network again
-    await Promise.all([
-      ...fresh.trips.map(t => upsertTrip(t)),
-      ...fresh.archivedTrips.map(t => upsertTrip(t)),
-    ]).catch(() => {})
     return { ...fresh, refresh: Promise.resolve(null) }
   },