fix(weixin): replace aiohttp ClientTimeout with asyncio.wait_for in _api_post/_api_get

Cron delivery to WeChat fails with 'Timeout context manager should
be used inside a task' because _api_post and _api_get use aiohttp's
ClientTimeout directly.  When the cron scheduler calls send() via
asyncio.run_coroutine_threadsafe(), aiohttp cannot find a running
task and raises RuntimeError.

_upload_media, _download_bytes, and _download_remote_media already
use asyncio.wait_for() to avoid this.  Apply the same pattern to
_api_post and _api_get — the two remaining iLink API helpers that
still use the raw ClientTimeout approach.

This fixes cron delivery errors seen on the WeChat platform adapter
when meyo-external cron jobs attempt to deliver output to WeChat.

gateway/platforms/weixin.py

@@ -378,12 +378,16 @@ async def _api_post(
 ) -> Dict[str, Any]:
     body = _json_dumps({**payload, "base_info": _base_info()})
     url = f"{base_url.rstrip('/')}/{endpoint}"
-    timeout = aiohttp.ClientTimeout(total=timeout_ms / 1000)
-    async with session.post(url, data=body, headers=_headers(token, body), timeout=timeout) as response:
-        raw = await response.text()
-        if not response.ok:
-            raise RuntimeError(f"iLink POST {endpoint} HTTP {response.status}: {raw[:200]}")
-        return json.loads(raw)
+    # Use asyncio.wait_for() instead of aiohttp ClientTimeout to avoid
+    # "Timeout context manager should be used inside a task" errors when
+    # invoked via asyncio.run_coroutine_threadsafe() from cron jobs.
+    async def _do() -> Dict[str, Any]:
+        async with session.post(url, data=body, headers=_headers(token, body)) as response:
+            raw = await response.text()
+            if not response.ok:
+                raise RuntimeError(f"iLink POST {endpoint} HTTP {response.status}: {raw[:200]}")
+            return json.loads(raw)
+    return await asyncio.wait_for(_do(), timeout=timeout_ms / 1000)
 
 
 async def _api_get(
@@ -398,12 +402,16 @@ async def _api_get(
         "iLink-App-Id": ILINK_APP_ID,
         "iLink-App-ClientVersion": str(ILINK_APP_CLIENT_VERSION),
     }
-    timeout = aiohttp.ClientTimeout(total=timeout_ms / 1000)
-    async with session.get(url, headers=headers, timeout=timeout) as response:
-        raw = await response.text()
-        if not response.ok:
-            raise RuntimeError(f"iLink GET {endpoint} HTTP {response.status}: {raw[:200]}")
-        return json.loads(raw)
+    # Use asyncio.wait_for() instead of aiohttp ClientTimeout to avoid
+    # "Timeout context manager should be used inside a task" errors when
+    # invoked via asyncio.run_coroutine_threadsafe() from cron jobs.
+    async def _do() -> Dict[str, Any]:
+        async with session.get(url, headers=headers) as response:
+            raw = await response.text()
+            if not response.ok:
+                raise RuntimeError(f"iLink GET {endpoint} HTTP {response.status}: {raw[:200]}")
+            return json.loads(raw)
+    return await asyncio.wait_for(_do(), timeout=timeout_ms / 1000)
 
 
 async def _get_updates(