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/indexer/src/main.rs

@@ -30,11 +30,7 @@ async fn async_main() -> anyhow::Result<()> {
         .connect(&config.database_url)
         .await?;
 
-    let state = AppState {
-        pool,
-        meili_url: config.meili_url.clone(),
-        meili_master_key: config.meili_master_key.clone(),
-    };
+    let state = AppState { pool };
 
     tokio::spawn(indexer::worker::run_worker(state.clone(), config.scan_interval_seconds));