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/static/app.css

@@ -0,0 +1,93 @@
+/* ImpTune layout — supplements Pico CSS */
+
+.layout {
+  display: flex;
+  min-height: 100vh;
+}
+
+/* Sidebar */
+.sidebar {
+  width: 220px;
+  flex-shrink: 0;
+  border-right: 1px solid var(--pico-muted-border-color, #e0e0e0);
+  padding: 1rem 0;
+  display: flex;
+  flex-direction: column;
+}
+
+.sidebar-brand {
+  padding: 0.5rem 1rem 1rem;
+  font-size: 1.1rem;
+  border-bottom: 1px solid var(--pico-muted-border-color, #e0e0e0);
+  margin-bottom: 0.5rem;
+}
+
+.sidebar-nav {
+  list-style: none;
+  padding: 0;
+  margin: 0;
+}
+
+.sidebar-nav li {
+  margin: 0;
+}
+
+.sidebar-nav a {
+  display: block;
+  padding: 0.6rem 1rem;
+  text-decoration: none;
+  color: inherit;
+  font-weight: 400;
+}
+
+.sidebar-nav a:hover {
+  background-color: var(--pico-secondary-background, rgba(0,0,0,0.05));
+}
+
+.sidebar-nav a.active {
+  font-weight: 600;
+  background-color: var(--pico-primary-background, rgba(0,0,0,0.08));
+  border-left: 3px solid var(--pico-primary, #1a73e8);
+}
+
+/* Main content */
+.main-content {
+  flex: 1;
+  padding: 1.5rem;
+  overflow-y: auto;
+}
+
+/* Quick action buttons */
+.quick-actions {
+  display: flex;
+  gap: 0.75rem;
+  margin-bottom: 1.5rem;
+  flex-wrap: wrap;
+}
+
+.btn-action {
+  display: inline-block;
+  padding: 0.5rem 1rem;
+  border: 1px solid var(--pico-primary, #1a73e8);
+  border-radius: 4px;
+  text-decoration: none;
+  color: var(--pico-primary, #1a73e8);
+  font-weight: 500;
+}
+
+.btn-action[aria-disabled="true"] {
+  opacity: 0.5;
+  cursor: not-allowed;
+  pointer-events: none;
+}
+
+/* Empty state */
+.empty-state {
+  color: var(--pico-muted-color, #666);
+  font-style: italic;
+}
+
+/* Recent activity */
+.activity-section {
+  margin-bottom: 1.5rem;
+}