fix: harden webhook reliability, fix bugs, add test suite

- Statuspage webhook always returns 200 to prevent subscriber removal
- Fix parseKvKey returning string chatId instead of number
- Queue consumer retries on Telegram 5xx instead of acking (prevents message loss)
- Fix observability top-level enabled flag (false → true)
- Add defensive null checks for webhook payload body
- Cache Bot instance per isolate to avoid middleware rebuild per request
- Add vitest + @cloudflare/vitest-pool-workers with 31 tests
- Document DLQ and KV sharding as declined features

vitest.config.js

@@ -0,0 +1,22 @@
+import { defineConfig } from "vitest/config";
+import { cloudflarePool, cloudflareTest } from "@cloudflare/vitest-pool-workers";
+
+export default defineConfig({
+  plugins: [
+    cloudflareTest({
+      wrangler: { configPath: "./wrangler.jsonc" },
+      miniflare: {
+        // Override remote KV with local-only for tests
+        kvNamespaces: ["claude_status"],
+      },
+    }),
+  ],
+  test: {
+    pool: cloudflarePool({
+      wrangler: { configPath: "./wrangler.jsonc" },
+      miniflare: {
+        kvNamespaces: ["claude_status"],
+      },
+    }),
+  },
+});