feat(01-01): create Docker scaffold, FastAPI app shell, and sidebar templates

- Dockerfile with python:3.12-slim-bookworm, curl downloads Pico CSS, HTMX, Alpine.js at build time
- docker-compose.yml with imptune_data:/data named volume and restart policy
- requirements.txt with all phase 1-5 dependencies
- imptune/config.py loading DATA_DIR/PORT from env with DB_PATH and DRIVERS_DIR derived paths
- imptune/main.py: FastAPI app with StaticFiles mount, health+pages routers, startup dir creation
- imptune/api/health.py: GET /health returning {"status": "ok"}
- imptune/api/pages.py: GET / returning dashboard.html with sync def handler
- imptune/templates/base.html: data-theme="auto", sidebar with 5 nav sections, /static/ paths only
- imptune/templates/dashboard.html: quick actions + empty state recent activity
- imptune/static/app.css: sidebar layout, active link highlight, quick action buttons

imptune/config.py

@@ -0,0 +1,12 @@
+import os
+from pathlib import Path
+
+from dotenv import load_dotenv
+
+load_dotenv()
+
+DATA_DIR = os.environ.get("DATA_DIR", "/data")
+PORT = int(os.environ.get("PORT", "8000"))
+
+DB_PATH = str(Path(DATA_DIR) / "imptune.db")
+DRIVERS_DIR = str(Path(DATA_DIR) / "drivers")