add http API, channel-driven life loop, predefined diary timer

- Extract http.rs: unified HTTP server with /api/timers and gitea webhook
- Life loop: select! on interval tick + mpsc channel for force-fire
- Predefined diary timer (cron 22:55 daily), auto-registered on startup
- BufferOutput for system timers (chat_id=0), no TG message
- state: ensure_timer(), get_timer()
- context.md: add blog and Hugo docs for AI

src/gitea.rs

@@ -151,27 +151,13 @@ pub struct WebhookState {
     pub bot_user: String,
 }
 
-pub async fn start_webhook_server(config: &GiteaConfig, bot_user: String) {
+pub fn webhook_router(config: &GiteaConfig, bot_user: String) -> axum::Router<()> {
     let gitea = GiteaClient::new(config);
-    let state = Arc::new(WebhookState {
-        gitea,
-        bot_user,
-    });
+    let state = Arc::new(WebhookState { gitea, bot_user });
 
-    let app = axum::Router::new()
+    axum::Router::new()
         .route("/webhook/gitea", post(handle_webhook))
-        .with_state(state);
-
-    let addr = format!("0.0.0.0:{}", config.webhook_port);
-    info!("gitea webhook server listening on {addr}");
-
-    let listener = tokio::net::TcpListener::bind(&addr)
-        .await
-        .unwrap_or_else(|e| panic!("bind {addr}: {e}"));
-
-    if let Err(e) = axum::serve(listener, app).await {
-        error!("webhook server error: {e}");
-    }
+        .with_state(state)
 }
 
 async fn handle_webhook(