refactor: replace Meilisearch with PostgreSQL full-text search

Remove Meilisearch dependency entirely. Search is now handled by
PostgreSQL ILIKE with pg_trgm indexes, joining series_metadata for
series-level authors. No external search engine needed.

- Replace search.rs Meilisearch HTTP calls with PostgreSQL queries
- Remove meili.rs from indexer, sync_meili call from job pipeline
- Remove MEILI_URL/MEILI_MASTER_KEY from config, state, env files
- Remove meilisearch service from docker-compose.yml
- Add migration 0027: drop sync_metadata, enable pg_trgm, add indexes
- Remove search resync button/endpoint (no longer needed)
- Update all documentation (CLAUDE.md, README.md, AGENTS.md, PLAN.md)

API contract unchanged — same SearchResponse shape returned.

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

apps/api/src/main.rs

@@ -68,8 +68,6 @@ async fn main() -> anyhow::Result<()> {
     let state = AppState {
         pool,
         bootstrap_token: Arc::from(config.api_bootstrap_token),
-        meili_url: Arc::from(config.meili_url),
-        meili_master_key: Arc::from(config.meili_master_key),
         page_cache: Arc::new(Mutex::new(LruCache::new(NonZeroUsize::new(512).expect("non-zero")))),
         page_render_limit: Arc::new(Semaphore::new(concurrent_renders)),
         metrics: Arc::new(Metrics::new()),