Optimize performance: batch DB ops, N+1 fixes, Suspense streaming, and Jotai best practices

- Add composite indexes on userEpisodeWatches and userMovieWatches for hot queries
- Batch episode tracking: wrap season/batch watches in single transaction (~8 queries vs 8*N)
- Fix N+1 patterns in credits, recommendations, and filmography with batch prefetch+insert
- Stream TV season hydration via Suspense instead of blocking page render
- Optimize webhook logs (per-connection LIMIT 10) and system health queries
- Merge genre filter waterfalls into single Promise.all fetch
- Migrate deprecated Jotai loadable() to unwrap()
- Replace isolated createStore()+Provider with useHydrateAtoms on root store
- Remove unnecessary atomWithStorage SSR guards (handled by Jotai internally)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

lib/actions/titles.ts

@@ -7,6 +7,7 @@ import { db } from "@/lib/db/client";
 import { episodes } from "@/lib/db/schema";
 import {
   logEpisodeWatch,
+  logEpisodeWatchBatch,
   logMovieWatch,
   markAllEpisodesWatched,
   rateTitleStars,
@@ -67,9 +68,10 @@ export async function watchSeason(seasonId: string) {
     .from(episodes)
     .where(eq(episodes.seasonId, seasonId))
     .all();
-  for (const ep of seasonEps) {
-    logEpisodeWatch(userId, ep.id);
-  }
+  logEpisodeWatchBatch(
+    userId,
+    seasonEps.map((ep) => ep.id),
+  );
 }
 
 export async function unwatchSeasonAction(seasonId: string) {
@@ -79,7 +81,5 @@ export async function unwatchSeasonAction(seasonId: string) {
 
 export async function batchWatchEpisodes(episodeIds: string[]) {
   const userId = await getSessionUserId();
-  for (const id of episodeIds) {
-    logEpisodeWatch(userId, id);
-  }
+  logEpisodeWatchBatch(userId, episodeIds);
 }