feat(gateway): add Feishu/Lark platform support (#3817)

Adds Feishu (ByteDance's enterprise messaging platform) as a gateway
platform adapter with full feature parity: WebSocket + webhook transports,
message batching, dedup, rate limiting, rich post/card content parsing,
media handling (images/audio/files/video), group @mention gating,
reaction routing, and interactive card button support.

Cherry-picked from PR #1793 by penwyp with:
- Moved to current main (PR was 458 commits behind)
- Fixed _send_with_retry shadowing BasePlatformAdapter method (renamed to
  _feishu_send_with_retry to avoid signature mismatch crash)
- Fixed import structure: aiohttp/websockets imported independently of
  lark_oapi so they remain available when SDK is missing
- Fixed get_hermes_home import (hermes_constants, not hermes_cli.config)
- Added skip decorators for tests requiring lark_oapi SDK
- All 16 integration points added surgically to current main

New dependency: lark-oapi>=1.5.3,<2 (optional, pip install hermes-agent[feishu])

Fixes #1788

Co-authored-by: penwyp <penwyp@users.noreply.github.com>

tests/gateway/test_unauthorized_dm_behavior.py

@@ -19,7 +19,7 @@ def _clear_auth_env(monkeypatch) -> None:
         "SMS_ALLOWED_USERS",
         "MATTERMOST_ALLOWED_USERS",
         "MATRIX_ALLOWED_USERS",
-        "DINGTALK_ALLOWED_USERS",
+        "DINGTALK_ALLOWED_USERS", "FEISHU_ALLOWED_USERS",
         "GATEWAY_ALLOWED_USERS",
         "TELEGRAM_ALLOW_ALL_USERS",
         "DISCORD_ALLOW_ALL_USERS",
@@ -30,7 +30,7 @@ def _clear_auth_env(monkeypatch) -> None:
         "SMS_ALLOW_ALL_USERS",
         "MATTERMOST_ALLOW_ALL_USERS",
         "MATRIX_ALLOW_ALL_USERS",
-        "DINGTALK_ALLOW_ALL_USERS",
+        "DINGTALK_ALLOW_ALL_USERS", "FEISHU_ALLOW_ALL_USERS",
         "GATEWAY_ALLOW_ALL_USERS",
     ):
         monkeypatch.delenv(key, raising=False)