feat(api): song search endpoint and PATCH /songs/{id}

GET /bands/{id}/songs/search — filter by title (ILIKE), tags (contains
all), key, BPM range, session_id. All params optional and composable.
PATCH /songs/{id} — update title, status, notes, tags, key, BPM.

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

api/src/rehearsalhub/repositories/song.py

@@ -1,6 +1,7 @@
 from __future__ import annotations
 
 import uuid
+from typing import Any
 
 from sqlalchemy import select
 from sqlalchemy.orm import selectinload
@@ -41,6 +42,43 @@ class SongRepository(BaseRepository[Song]):
         result = await self.session.execute(stmt)
         return result.scalar_one_or_none()
 
+    async def search(
+        self,
+        band_id: uuid.UUID,
+        q: str | None = None,
+        tags: list[str] | None = None,
+        key: str | None = None,
+        bpm_min: float | None = None,
+        bpm_max: float | None = None,
+        session_id: uuid.UUID | None = None,
+    ) -> list[Song]:
+        from sqlalchemy import cast, func
+        from sqlalchemy.dialects.postgresql import ARRAY
+        from sqlalchemy import Text
+
+        stmt = (
+            select(Song)
+            .where(Song.band_id == band_id)
+            .options(selectinload(Song.versions))
+            .order_by(Song.updated_at.desc())
+        )
+        if q:
+            stmt = stmt.where(Song.title.ilike(f"%{q}%"))
+        if tags:
+            # songs.tags must contain ALL requested tags
+            stmt = stmt.where(Song.tags.contains(cast(tags, ARRAY(Text))))
+        if key:
+            stmt = stmt.where(func.lower(Song.global_key) == key.lower())
+        if bpm_min is not None:
+            stmt = stmt.where(Song.global_bpm >= bpm_min)
+        if bpm_max is not None:
+            stmt = stmt.where(Song.global_bpm <= bpm_max)
+        if session_id is not None:
+            stmt = stmt.where(Song.session_id == session_id)
+
+        result = await self.session.execute(stmt)
+        return list(result.scalars().all())
+
     async def next_version_number(self, song_id: uuid.UUID) -> int:
         from sqlalchemy import func