feat: implement Telegram bot for Claude status webhooks

Cloudflare Workers bot that forwards status.claude.com (Atlassian
Statuspage) incident and component updates to subscribed Telegram
users via CF Queues fan-out.

- Hono.js routing with grammY webhook handler
- Bot commands: /start, /stop, /status, /subscribe
- Supergroup topic support (message_thread_id)
- KV store with claude-status: prefix and composite keys
- Queue consumer with batch send, 403 auto-removal, 429 retry
- Timing-safe webhook secret validation
- HTML escaping for Telegram messages

src/kv-store.js

@@ -0,0 +1,84 @@
+const KV_KEY = "claude-status:subscribers";
+
+/**
+ * Build composite key: "chatId" or "chatId:threadId" for supergroup topics
+ */
+export function buildSubscriberKey(chatId, threadId) {
+  return threadId != null ? `${chatId}:${threadId}` : `${chatId}`;
+}
+
+/**
+ * Parse composite key back into { chatId, threadId }
+ */
+export function parseSubscriberKey(key) {
+  const parts = key.split(":");
+  if (parts.length >= 2 && parts[0].startsWith("-")) {
+    // Supergroup IDs start with "-100", so key is "-100xxx:threadId"
+    // Find the last ":" — everything before is chatId, after is threadId
+    const lastColon = key.lastIndexOf(":");
+    return {
+      chatId: key.slice(0, lastColon),
+      threadId: parseInt(key.slice(lastColon + 1), 10),
+    };
+  }
+  return { chatId: key, threadId: null };
+}
+
+/**
+ * Get all subscribers from KV
+ */
+export async function getSubscribers(kv) {
+  const data = await kv.get(KV_KEY, "json");
+  return data || {};
+}
+
+/**
+ * Write all subscribers to KV
+ */
+async function setSubscribers(kv, data) {
+  await kv.put(KV_KEY, JSON.stringify(data));
+}
+
+/**
+ * Add subscriber with default types
+ */
+export async function addSubscriber(kv, chatId, threadId, types = ["incident", "component"]) {
+  const subs = await getSubscribers(kv);
+  const key = buildSubscriberKey(chatId, threadId);
+  subs[key] = { types };
+  await setSubscribers(kv, subs);
+}
+
+/**
+ * Remove subscriber
+ */
+export async function removeSubscriber(kv, chatId, threadId) {
+  const subs = await getSubscribers(kv);
+  const key = buildSubscriberKey(chatId, threadId);
+  delete subs[key];
+  await setSubscribers(kv, subs);
+}
+
+/**
+ * Update subscriber's notification type preferences
+ */
+export async function updateSubscriberTypes(kv, chatId, threadId, types) {
+  const subs = await getSubscribers(kv);
+  const key = buildSubscriberKey(chatId, threadId);
+  if (!subs[key]) {
+    subs[key] = { types };
+  } else {
+    subs[key].types = types;
+  }
+  await setSubscribers(kv, subs);
+}
+
+/**
+ * Get subscribers filtered by event type, returns [{ chatId, threadId }, ...]
+ */
+export async function getSubscribersByType(kv, eventType) {
+  const subs = await getSubscribers(kv);
+  return Object.entries(subs)
+    .filter(([, val]) => val.types.includes(eventType))
+    .map(([key]) => parseSubscriberKey(key));
+}