feat(simkl): comply with Simkl API conventions across Android, web, and proxies

[Himanth-reddy]

Summary

This PR aligns all Simkl API calls across ARVIO with the official Simkl Headers and Parameters Conventions so requests are correctly identified and visible in Simkl's API Debug & Analytics dashboard.

Changes

• Query Parameters: Ensure client_id, app-name=arvio, and app-version are appended to all Simkl requests (public catalog, scrobble, and sync) rather than only /oauth/pin.
• Case Sensitivity: Enforce lowercase app-name=arvio per Simkl specification.
• User-Agent: Add descriptive User-Agent headers across Android, Web, Netlify functions, and Supabase Edge functions.
• Proxy Handlers: Update Netlify _backend.js and Supabase simkl-proxy to preserve/forward client_id, app-name, and app-version query parameters and User-Agent on all outgoing calls.
• Tests: Added automated test to simkl-proxy.test.js validating that required query parameters and headers are attached to all proxied requests.

[Himanth-reddy]

Simkl Official Integration Review Remediation

This commit addresses all findings and recommendations from the official Simkl integration review across Android, Web, Netlify functions, and Supabase Edge Functions:

P0 — Request Volume & Sync Storm Prevention

• Strict /sync/activities Gating:
  • SimklSyncService.kt and simkl.ts now gate all library syncs behind /sync/activities. If activities.all matches the locally stored watermark, sync is completely skipped—even when force=true.
• Continuous Delta Sync (date_from):
  • Reserved 3-part sequential category sync (movies → shows → anime → playback) for initial sync only.
  • Subsequent syncs use GET /sync/all-items?date_from={watermark} to fetch deltas and merge changes into the existing snapshot (mergeMovieRows, mergeShowRows).
• Watermark & Snapshot Disk Persistence:
  • Added simkl_sync_watermark persistence to profile-scoped DataStore (SyncProviderStore.kt) and cached snapshots to disk (simkl_snapshot_cache.json), ensuring state survives process death.
  • Eliminated aggressive window focus cache invalidation in Web; caches persist in localStorage and only invalidate upon account/token change.

P1 — Data Loss Prevention & Scrobbler Heuristics

• Removed Progress Multiplier Bug:
  • Removed progress <= 1 ? progress * 100 logic across Android (SimklScrobbler.kt) and Web (simkl.ts). Small progress percentages (e.g. 0.5%–1.0%) are preserved accurately and clamped between 0 and 100.
• Movie Unmark Without Rating/Library Erasure:
  • Unmarking a movie from watched now calls POST /sync/add-to-list with to: "plantowatch" instead of /sync/history/remove, preventing Simkl from purging the item row and user rating.
• FIFO Scrobble Command Queue:
  • Added a FIFO queue in SimklScrobbler.kt to ensure rapid playback transitions (auto-advance / next episode) execute STOP before START without dropping commands.
• Player Exit Watched Threshold (≥ 80%):
  • Exiting playback at ≥ 80% progress sends scrobbleStop instead of pause, enabling Simkl to mark the item as completed.
• Anime Path A Standardized:
  • Scrobbles and history sync for anime now consistently send show with use_tvdb_anime_seasons: true and request extended=full_anime_seasons during full anime sync.
• Batched Season Marking:
  • Marking a whole season watched in Web (DetailsDrawer.tsx) sends a single batched POST /sync/history payload with seasons: [{ number: seasonNumber }] instead of N individual episode calls.

P2 — Compliance, Proxy Allowlists & Resilience

• Proxy Endpoint Expansion:
  • Added allowlist rules for bare GET /sync/all-items, GET /sync/playback/episodes, and DELETE /sync/playback/{id} across Web API route, Netlify proxy, and Supabase Edge Function.
• Header & Error Resilience:
  • Proxies forward upstream Retry-After headers on HTTP 429.
  • Added interceptor logging for HTTP 429 and HTTP 412 (client_id_failed) responses.
  • Deducted not_aired_episodes_count from total episode counts when computing progress.
  • Added support for ids.slug and alternate ids.simkl_id keys, plus a Simkl badge on the Web details drawer linking to simkl.com.
  • Terminated polling loops immediately when KO or device_code is returned.

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Verification

• Android: 26/26 tests passed in SimklIntegrationTest.kt (./gradlew testPlayDebugUnitTest --tests "com.arflix.tv.data.repository.simkl.*").
• Netlify: 58/58 tests passed (npm --prefix netlify-auth-site test).
• Web: 51/51 tests passed (npm --prefix web test).
• Web Build: Production build succeeded cleanly (npm --prefix web run build).