fix: make docker compose build and start the API

The image context was backend/, so COPY frontend/ failed. Build from the
repo root, place Python modules on the import path, and pin packages that
exist on PyPI. The web process no longer loads the LLM at startup.

backend/app/models/__init__.py

@@ -1 +1,38 @@
-# Pydantic models package
+from typing import Dict, List, Optional
+
+from pydantic import BaseModel
+
+
+class ChatRequest(BaseModel):
+    message: str
+    top_k: int = 3
+
+
+class ChatResponse(BaseModel):
+    query: str
+    response: str
+    sources: List[Dict]
+
+
+class BookInfo(BaseModel):
+    title: str
+    source: str
+
+
+class UploadResponse(BaseModel):
+    message: str
+    filename: str
+
+
+class ScheduleInfo(BaseModel):
+    id: int
+    time: str
+    book: Optional[str] = None
+    enabled: bool
+    next_run: Optional[str] = None
+
+
+class ScheduleRequest(BaseModel):
+    time: str
+    book: Optional[str] = None
+    enabled: bool = True