feat: analysis providers, settings UI, song search, WAV duration fix

- Multi-provider AI analysis (Anthropic, OpenAI, Ollama, Algorithmic)
- server-only guards on all provider files; client bundle fix
- /settings page with provider status, Ollama model picker, preferences
- Song search box on /analyze replacing raw MBID input (debounced, keyboard nav)
- Auto-register song via MusicBrainz on POST /api/tracks (no more 404)
- Fix WAV duration bug: last section songEnd was double-counting elapsed time
- Registry sync comment updated for self-hosted HTTPS git servers

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

lib/db/client.ts

@@ -68,6 +68,11 @@ export interface SongRow {
   updated_at: Date;
 }
 
+export async function getSongByMbid(mbid: string): Promise<SongRow | null> {
+  const { rows } = await query<SongRow>("SELECT * FROM songs WHERE mbid = $1", [mbid]);
+  return rows[0] ?? null;
+}
+
 export async function searchSongs(q: string, limit = 20): Promise<SongRow[]> {
   const { rows } = await query<SongRow>(
     `SELECT * FROM songs