Convert to Flask app with password-protected admin panel

Links now live in data/links.json instead of hardcoded HTML, editable
via /admin (add/rename/reorder/delete sections and links, per-link
color and half-width side-by-side layout). New pages can be added
without code changes. Docker image only needs rebuilding on code
changes now, not on content changes (data/ is volume-mounted).

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

docker-compose.yml

@@ -0,0 +1,13 @@
+services:
+  honey-links:
+    build: .
+    ports:
+      - "8080:80"
+    environment:
+      - ADMIN_PASSWORD=${ADMIN_PASSWORD}
+      - SECRET_KEY=${SECRET_KEY}
+      # Set to "false" only for local http-only testing without a TLS proxy in front.
+      - COOKIE_SECURE=${COOKIE_SECURE:-true}
+    volumes:
+      - ./data:/app/data
+    restart: unless-stopped