feat: Add album artwork support

- Backend: artwork_filename column on clips table (auto-migration)
- Backend: PATCH /api/clips/{id}/artwork (upload image, 5MB limit)
- Backend: GET /api/clips/{id}/artwork (serve image with correct content-type)
- Backend: DELETE /api/clips/{id}/artwork (remove artwork file + null out DB)
- Backend: DELETE /api/clips/{id} now cascade-removes artwork file
- Frontend: Clip interface includes artwork_filename
- Frontend: Gallery ribbons show artwork thumbnail with hover overlay (play + upload)
- Frontend: Gallery tiles show artwork with hover overlay (play + upload)
- Frontend: DetailPanel shows full artwork with upload/change/remove controls
- Frontend: App.tsx handleUploadArtwork + handleRemoveArtwork handlers
- Storage: /data/artwork/ directory for image files

backend/src/models.py

@@ -1,11 +1,44 @@
-from pydantic import BaseModel
+from pydantic import BaseModel, field_validator
 from datetime import datetime
 from typing import Optional
 
+# Supported models and their constraints
+LYRIA_MODELS = {
+    "lyria-3-clip-preview": {
+        "name": "Clip Preview",
+        "max_duration": 30,
+        "default_duration": 30,
+        "description": "30-second clip, fastest generation",
+    },
+    "lyria-3-pro-preview": {
+        "name": "Pro",
+        "max_duration": 184,
+        "default_duration": 120,
+        "description": "Full songs up to ~3 min, structure-aware",
+    },
+}
+
+DEFAULT_MODEL = "lyria-3-clip-preview"
+
 class GenerateRequest(BaseModel):
     prompt: str
-    model: str = "lyria-3-clip-preview"
-    duration: int = 30
+    model: str = DEFAULT_MODEL
+    duration: Optional[int] = None  # defaults to model default
+
+    @field_validator('model')
+    @classmethod
+    def validate_model(cls, v):
+        v = v.strip()
+        if v not in LYRIA_MODELS:
+            valid = ', '.join(LYRIA_MODELS.keys())
+            raise ValueError(f"Unknown model '{v}'. Supported: {valid}")
+        return v
+
+    def get_effective_duration(self) -> int:
+        """Return duration clamped to model limits, defaulting to model default if not specified."""
+        info = LYRIA_MODELS[self.model]
+        dur = self.duration if self.duration is not None else info["default_duration"]
+        return min(dur, info["max_duration"])
 
 class GenerateResponse(BaseModel):
     id: str
@@ -14,15 +47,20 @@ class GenerateResponse(BaseModel):
 
 class Clip(BaseModel):
     id: str
+    title: Optional[str] = None
     prompt: str
     model: str
     duration_seconds: int
     filename: str
+    artwork_filename: Optional[str] = None
     file_size_bytes: Optional[int] = None
     status: str
     error_message: Optional[str] = None
     created_at: datetime
 
+class RenameRequest(BaseModel):
+    title: str
+
 class ClipList(BaseModel):
     clips: list[Clip]
-    total: int
+    total: int