feat(obs): enable Workers Observability (logs + traces)

- wrangler.toml: [observability] block with logs + traces at
  head_sampling_rate=1 (200k free events/day on free plan).
- src/index.js: structured request log emitted on every fetch
  (method/path/status/ms) — JSON shape so Observability's filter UI
  can index individual fields.
- Refactored fetch body into a route() helper so the log line sees the
  final response status.

src/index.js

@@ -56,25 +56,46 @@ export default {
    * @param {any} _ctx
    */
   async fetch(request, env, _ctx) {
+    const start = Date.now();
     const { pathname } = new URL(request.url);
+    const method = request.method;
 
-    if (request.method === "GET" && pathname === "/") {
-      return new Response("miti99bot ok", {
-        status: 200,
-        headers: { "content-type": "text/plain" },
-      });
-    }
+    const response = await route(request, env, pathname);
 
-    if (request.method === "POST" && pathname === "/webhook") {
-      try {
-        const handler = await getWebhookHandler(env);
-        return await handler(request);
-      } catch (err) {
-        console.error("webhook handler failed", err);
-        return new Response("internal error", { status: 500 });
-      }
-    }
-
-    return new Response("not found", { status: 404 });
+    // Structured request log for Workers Observability dashboard.
+    console.log(JSON.stringify({
+      msg: "req",
+      method,
+      path: pathname,
+      status: response.status,
+      ms: Date.now() - start,
+    }));
+    return response;
   },
 };
+
+/**
+ * @param {Request} request
+ * @param {any} env
+ * @param {string} pathname
+ */
+async function route(request, env, pathname) {
+  if (request.method === "GET" && pathname === "/") {
+    return new Response("miti99bot ok", {
+      status: 200,
+      headers: { "content-type": "text/plain" },
+    });
+  }
+
+  if (request.method === "POST" && pathname === "/webhook") {
+    try {
+      const handler = await getWebhookHandler(env);
+      return await handler(request);
+    } catch (err) {
+      console.error("webhook handler failed", err);
+      return new Response("internal error", { status: 500 });
+    }
+  }
+
+  return new Response("not found", { status: 404 });
+}

wrangler.toml

@@ -35,6 +35,22 @@ database_id = "261b54e7-0fdb-4fe7-8ed9-2e8a8bcf459c"
 [triggers]
 crons = ["0 17 * * *"]
 
+# Workers Observability — captures console.* logs, request metadata, and
+# invocation traces in the Cloudflare dashboard (Observability → Logs).
+# 200k events/day included on free plan. `head_sampling_rate = 1` keeps
+# all invocations; drop to 0.1 for 10% sampling if volume grows.
+[observability]
+enabled = true
+head_sampling_rate = 1
+
+[observability.logs]
+enabled = true
+invocation_logs = true
+
+[observability.traces]
+enabled = true
+head_sampling_rate = 1
+
 # Secrets (set via `wrangler secret put <name>`, NOT in this file):
 #   TELEGRAM_BOT_TOKEN       — bot token from @BotFather
 #   TELEGRAM_WEBHOOK_SECRET  — arbitrary high-entropy string, also set in .env.deploy