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>

gateway/config.py

@@ -57,6 +57,7 @@ class Platform(Enum):
     DINGTALK = "dingtalk"
     API_SERVER = "api_server"
     WEBHOOK = "webhook"
+    FEISHU = "feishu"
 
 
 @dataclass
@@ -274,6 +275,9 @@ class GatewayConfig:
             # Webhook uses enabled flag only (secrets are per-route)
             elif platform == Platform.WEBHOOK:
                 connected.append(platform)
+            # Feishu uses extra dict for app credentials
+            elif platform == Platform.FEISHU and config.extra.get("app_id"):
+                connected.append(platform)
         return connected
     
     def get_home_channel(self, platform: Platform) -> Optional[HomeChannel]:
@@ -810,6 +814,33 @@ def _apply_env_overrides(config: GatewayConfig) -> None:
         if webhook_secret:
             config.platforms[Platform.WEBHOOK].extra["secret"] = webhook_secret
 
+    # Feishu / Lark
+    feishu_app_id = os.getenv("FEISHU_APP_ID")
+    feishu_app_secret = os.getenv("FEISHU_APP_SECRET")
+    if feishu_app_id and feishu_app_secret:
+        if Platform.FEISHU not in config.platforms:
+            config.platforms[Platform.FEISHU] = PlatformConfig()
+        config.platforms[Platform.FEISHU].enabled = True
+        config.platforms[Platform.FEISHU].extra.update({
+            "app_id": feishu_app_id,
+            "app_secret": feishu_app_secret,
+            "domain": os.getenv("FEISHU_DOMAIN", "feishu"),
+            "connection_mode": os.getenv("FEISHU_CONNECTION_MODE", "websocket"),
+        })
+        feishu_encrypt_key = os.getenv("FEISHU_ENCRYPT_KEY", "")
+        if feishu_encrypt_key:
+            config.platforms[Platform.FEISHU].extra["encrypt_key"] = feishu_encrypt_key
+        feishu_verification_token = os.getenv("FEISHU_VERIFICATION_TOKEN", "")
+        if feishu_verification_token:
+            config.platforms[Platform.FEISHU].extra["verification_token"] = feishu_verification_token
+        feishu_home = os.getenv("FEISHU_HOME_CHANNEL")
+        if feishu_home:
+            config.platforms[Platform.FEISHU].home_channel = HomeChannel(
+                platform=Platform.FEISHU,
+                chat_id=feishu_home,
+                name=os.getenv("FEISHU_HOME_CHANNEL_NAME", "Home"),
+            )
+
     # Session settings
     idle_minutes = os.getenv("SESSION_IDLE_MINUTES")
     if idle_minutes: