feat: add title-only search mode

Adds a titleOnly flag to page search: the Postgres driver matches
titles via trigram-indexed unaccented LIKE ranked by word_similarity,
and a Match filter in the search spotlight switches between everything
and title-only matching.

apps/server/src/database/migrations/20260824T211732-page-title-trgm-index.ts

@@ -0,0 +1,11 @@
+import { type Kysely, sql } from 'kysely';
+
+export async function up(db: Kysely<any>): Promise<void> {
+  await sql`CREATE INDEX IF NOT EXISTS pages_title_trgm_idx ON pages USING gin (lower(f_unaccent(title)) gin_trgm_ops)`.execute(
+    db,
+  );
+}
+
+export async function down(db: Kysely<any>): Promise<void> {
+  await sql`DROP INDEX IF EXISTS pages_title_trgm_idx`.execute(db);
+}