fix(trakt): first connect survives network drops and shows the full history at once

[ReichiMD]

Summary

Connecting Trakt for the first time went wrong in three places (reproduced on a phone with logcat, profile without a cloud account):

1. The first attempt failed with a raw Unable to resolve host "api.trakt.tv" toast. While the user approves the code in a browser, ARVIO sits in the background and the phone briefly loses DNS. The polling loop treated any error without an HTTP code as fatal and ended the sign-in.
2. The sync summary stayed empty for ~14 s. The silent full sync only started after the Continue Watching fetch (~10 s here).
3. Home showed only part of the ticks until the app was restarted. Right after the token the watched cache loaded 576 movies / 4152 episode keys from Trakt. After the sync it was reloaded from TraktSyncService.getWatchedMovies/Episodes(), which without a Supabase account return what the last full sync kept in memory. When a show was rewatched, that sync expands only the 15 most recent shows (useProgressExpansion), so the cache shrank to 1170 episode keys and Trakt was skipped because the list was not empty: Home went from 151 started shows to 15. Home was not told about the reload either, because COMPLETED goes out before it.

Changes

• Polling keeps going on network drops. isTransientTraktPollFailure: an IOException of the poll itself (DNS, timeout, dropped connection) no longer ends the activation. Only the poll is retried, not the work after the token is stored. Certificate failures are excluded because they do not heal by waiting. If the code runs out while the network stays down, the network error is reported instead of a plain expiry. A 409 right after such a failure (token issued, answer lost) reports that error instead of "code already used".
• The sync starts before the Continue Watching fetch. performFullSync runs in its own job anyway, so the summary no longer waits for Continue Watching. On the device the summary was filled ~5 s after the token instead of ~14 s.
• The watched cache reads Trakt whenever it is connected and merges it with the sync service's sets. With USE_NETLIFY_CLOUD_SYNC the Supabase reads are empty anyway, and without an account the in-memory sync result cannot stand in for the Trakt history.
• Home is told when the watched cache was reloaded after an invalidation (TraktRepository.watchedCacheReloaded, a small WatchedCacheReloads helper) and runs refreshWatchedBadges(immediate = true). The first load after start or a profile switch is not reported, because Home runs its own pass for it.
• Stale cache loads no longer win. A load overtaken by invalidateWatchedCache() or a profile switch used to mark the cache initialized with its old data. Now a generation counter keeps it from doing that, and a caller that waited for it loads the current state. The parallel sync made this more likely, and the reload event would have carried it to Home.

Notes, not changed here

• The sync summary still shows the sync's own count (585 episodes here vs. 4152 on Trakt). It comes from the same 15-show expansion. The first sync of a Supabase account would have the same gap.
• Without an account, the Trakt watched lists are now fetched again after each sync (the sync fetched them seconds before). That is one extra set of paged requests per sync. Reusing the sync's lists would be a larger change.
• The background TraktSyncWorker refreshes the in-memory list without invalidating the cache. This is unchanged.
• This touches HomeViewModel next to feat(home): show watched ticks without a Trakt sign-in #758, and the two merge without conflicts.

Testing

• New TraktWatchedCacheLoadTest (Robolectric): Trakt is read even when the sync left a partial list in memory. A load overtaken by an invalidation does not keep its old data. Both fail on main.
• New WatchedCacheReloadsTest: only a reload after an invalidation is reported, and a profile reset drops a pending one. TraktDeviceActivationTest: DNS, timeout and connect failures are transient; HTTP 404/410, missing credentials and certificate failures are not.
• testSideloadDebugUnitTest: 1823 tests, 0 failures.
• Test APK on a phone (fresh install, Trakt only, no cloud account), with temporary logcat lines on the test build only. Two DNS failures during polling, the sign-in still succeeded on the first attempt. Summary filled 4.9 s after the token. Watched cache after the sync: 576 movies / 4737 keys. Home ticked 11 cards right after the reload, without a restart.

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created by Claude (Anthropic) on behalf of @ReichiMD

[ProdigyV21]

Thanks for the Trakt reliability work. I kept the reconnect/history improvements and added serialized cache loading, stale profile/generation checks, independent provider fallback, and regression coverage. The combined batch passes 128 targeted unit tests and both Play/Sideload Kotlin compilation. Merging with your original commits and authorship preserved; live third-party account flows were not exercised.