Add read-only web UI

Serves Pete's classified-story archive over HTTP alongside the Matrix
bot. Three sections (gaming/tech/politics), Animal-Crossing-vibe Tailwind
templates, day/night palette driven by the visitor's browser clock.
Web port configurable via web.listen_addr and ${PETE_WEB_PORT} in
docker-compose. Tailwind built in a node stage in the Dockerfile so
deployments don't need node at runtime.

internal/web/static/img/leaf.svg

@@ -0,0 +1,4 @@
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 64 64">
+  <path d="M48 8C28 8 12 22 12 42c0 6 2 12 6 16 4-12 14-22 26-26-10 8-16 18-18 30 16 0 30-14 30-34 0-8-4-16-8-20z" fill="#6db73c" stroke="#3f6e1f" stroke-width="3" stroke-linejoin="round"/>
+  <path d="M22 52c8-12 18-20 30-26" stroke="#3f6e1f" stroke-width="2" fill="none" stroke-linecap="round"/>
+</svg>