feat: add SoundFont inspection engine + AI instrument schema

- SoundFontInspector (sf2utils) scans .sf2, generates full/condensed catalog
- GET /api/v1/plugins/soundfonts/catalog with lazy init + cache invalidation
- AI tool generate_multitrack_midi now requires soundfont_id/bank/program
- Condensed catalog auto-injected into AI system prompt with bank rules
- Server render: FluidSynth program_select uses bank/program + channel routing (drums→ch9)
- VST3 pedalboard path inserts CC0 bank select + program change before notes
- DecentSamplerManager loads .dspreset with CWD fix for relative sample paths
- Pianobook render branch in render_engine.py
- Client SonicSF: controllerChange, programChange, applyAITrackInstrument
- Post-AI track creation applies instrument via applyAITrackInstrument
- Background cache rescan on .sf2 upload, frontend re-fetches catalog
- libcurl4 + VST3 dirs in Dockerfile

app/api/v1/plugins.py

@@ -1,10 +1,11 @@
 import os, uuid, json, tempfile
-from fastapi import APIRouter, HTTPException, Depends, UploadFile, File
+from fastapi import APIRouter, HTTPException, Depends, UploadFile, File, BackgroundTasks
 from pydantic import BaseModel
 from typing import Optional, Any
 from app.config import settings
 from app.core.vst_engine import PluginManager, HAS_PEDALBOARD, HAS_PYFLUIDSYNTH
 from app.core.render_engine import PythonRenderEngine
+from app.core.soundfont_inspector import SoundFontInspector
 from app.api.v1.auth import get_current_user
 
 router = APIRouter()
@@ -12,6 +13,16 @@ router = APIRouter()
 UPLOAD_SF_DIR = os.path.join(settings.STORAGE_DIR, "soundfonts")
 os.makedirs(UPLOAD_SF_DIR, exist_ok=True)
 
+SYSTEM_SF_DIR = "/opt/daw_engine/soundfonts"
+
+_inspector = None
+
+def get_inspector():
+    global _inspector
+    if _inspector is None:
+        _inspector = SoundFontInspector(system_sf_dir=SYSTEM_SF_DIR, upload_sf_dir=UPLOAD_SF_DIR)
+    return _inspector
+
 
 @router.get("/available")
 async def list_plugins(current_user: dict = Depends(get_current_user)):
@@ -35,6 +46,14 @@ async def list_default_soundfonts():
     return result
 
 
+@router.get("/soundfonts/catalog")
+async def soundfont_catalog(current_user: dict = Depends(get_current_user)):
+    inspector = get_inspector()
+    full_catalog = inspector.get_catalog()
+    condensed_catalog = inspector.get_condensed_catalog_summary()
+    return {"full_catalog": full_catalog, "condensed_catalog": condensed_catalog}
+
+
 @router.get("/soundfont-instruments/{sf_id}")
 async def list_soundfont_instruments(sf_id: str, current_user: dict = Depends(get_current_user)):
     pm = PluginManager(upload_sf_dir=UPLOAD_SF_DIR)
@@ -45,6 +64,7 @@ async def list_soundfont_instruments(sf_id: str, current_user: dict = Depends(ge
 @router.post("/upload-soundfont")
 async def upload_soundfont(
     file: UploadFile = File(...),
+    background_tasks: BackgroundTasks = None,
     current_user: dict = Depends(get_current_user)
 ):
     if not (file.filename and (file.filename.endswith(".sf2") or file.filename.endswith(".sf3"))):
@@ -69,6 +89,11 @@ async def upload_soundfont(
         import json
         json.dump({"original_name": file.filename, "uuid": file_uuid, "file": file_id}, f)
 
+    inspector = get_inspector()
+    inspector.invalidate_catalog_cache()
+    if background_tasks:
+        background_tasks.add_task(inspector.generate_full_catalog)
+
     return {"id": file_id, "name": file.filename, "path": dest_path, "size_bytes": len(contents)}
 
 
@@ -93,6 +118,8 @@ async def delete_soundfont(sf_id: str, current_user: dict = Depends(get_current_
             break
     if not deleted:
         raise HTTPException(status_code=404, detail="SoundFont not found")
+    inspector = get_inspector()
+    inspector.invalidate_catalog_cache()
     return {"deleted": True, "sf_id": sf_id}