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/api/pages.py

@@ -0,0 +1,20 @@
+from fastapi import APIRouter, Request
+from fastapi.responses import HTMLResponse
+from fastapi.templating import Jinja2Templates
+from pathlib import Path
+
+router = APIRouter()
+
+templates = Jinja2Templates(directory=str(Path(__file__).parent.parent / "templates"))
+
+
+@router.get("/", response_class=HTMLResponse)
+def dashboard(request: Request):
+    return templates.TemplateResponse(
+        "dashboard.html",
+        {
+            "request": request,
+            "recent_printers": [],
+            "recent_packages": [],
+        },
+    )