feat(broker+cli): multi-tenant telegram bridge with 4 entry points

- DB: mesh.telegram_bridge table + migration
- Broker: telegram-bridge.ts (Grammy bot + WS pool + routing)
- Broker: telegram-token.ts (JWT connect tokens)
- Broker: POST /tg/token endpoint + bridge boot on startup
- CLI: claudemesh connect/disconnect telegram commands
- Spec: docs/telegram-bridge-spec.md

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

packages/db/migrations/0016_telegram-bridge.sql

@@ -0,0 +1,16 @@
+CREATE TABLE IF NOT EXISTS mesh.telegram_bridge (
+  id text PRIMARY KEY NOT NULL,
+  chat_id bigint NOT NULL,
+  chat_type text DEFAULT 'private',
+  chat_title text,
+  mesh_id text NOT NULL REFERENCES mesh.mesh(id) ON DELETE CASCADE ON UPDATE CASCADE,
+  member_id text REFERENCES mesh.member(id),
+  pubkey text NOT NULL,
+  secret_key text NOT NULL,
+  display_name text DEFAULT 'telegram',
+  active boolean DEFAULT true,
+  created_at timestamp DEFAULT now() NOT NULL,
+  disconnected_at timestamp
+);
+
+CREATE UNIQUE INDEX IF NOT EXISTS telegram_bridge_chat_mesh_idx ON mesh.telegram_bridge (chat_id, mesh_id);