Add connected clients popup per AP

Clicking an AP name opens a modal showing all wireless clients currently
associated with that AP: hostname/MAC, IP, SSID, band, channel, signal
strength with quality label, TX/RX link rate, and connection uptime.

Backend: GET /api/ap-clients?mac=&site_key= calls the Omada clients
endpoint with filters.apMac; falls back to client-side filtering if the
controller doesn't support that query param.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

app/omada.py

@@ -188,6 +188,27 @@ class OmadaClient:
                 return int(device.get("uptimeLong", 0))
         raise RuntimeError(f"AP {mac} not found in site {site_key}")
 
+    async def get_ap_clients(self, ap_mac: str, site_key: str) -> list[dict]:
+        """Fetch wireless clients currently connected to a specific AP."""
+        await self._ensure_ready()
+        norm_mac = ap_mac.upper().replace("-", ":")
+        try:
+            data = await self._request_with_retry(
+                "GET",
+                f"{OMADA_BASE_URL}/{self._omadac_id}/api/v2/sites/{site_key}/clients",
+                params={"page": 1, "pageSize": 200, "filters.active": "true", "filters.apMac": ap_mac},
+            )
+        except RuntimeError:
+            # Older firmware may not support filters.apMac — fall back and filter client-side
+            data = await self._request_with_retry(
+                "GET",
+                f"{OMADA_BASE_URL}/{self._omadac_id}/api/v2/sites/{site_key}/clients",
+                params={"page": 1, "pageSize": 200, "filters.active": "true"},
+            )
+        result = data.get("result", {})
+        clients = result.get("data", []) if isinstance(result, dict) else (result if isinstance(result, list) else [])
+        return [c for c in clients if c.get("apMac", "").upper().replace("-", ":") == norm_mac]
+
     async def reboot_ap(self, mac: str, site_key: str, min_uptime: int = 300) -> dict:
         await self._ensure_ready()
         uptime = await self._get_ap_uptime(mac, site_key)