Add last_posted date to /api/channel-list from Elasticsearch

Queries the latest video date per channel and includes it in the
channel-list JSON response.

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

search_app.py

@@ -1277,6 +1277,29 @@ def create_app(config: AppConfig = CONFIG) -> Flask:
         data.sort(key=lambda item: item["Name"].lower())
         return jsonify(data)
 
+    def _channel_latest_dates() -> Dict[str, Optional[str]]:
+        """Return {channel_id: latest_date_str} from Elasticsearch."""
+        try:
+            resp = client.search(index=index, body={
+                "size": 0,
+                "aggs": {
+                    "by_channel": {
+                        "terms": {"field": "channel_id.keyword", "size": 500},
+                        "aggs": {"latest": {"max": {"field": "date"}}},
+                    }
+                },
+            }, request_timeout=15)
+        except Exception as exc:
+            LOGGER.warning("Failed to fetch latest dates: %s", exc)
+            return {}
+        result: Dict[str, Optional[str]] = {}
+        for bucket in resp.get("aggregations", {}).get("by_channel", {}).get("buckets", []):
+            cid = bucket.get("key")
+            val = bucket.get("latest", {}).get("value_as_string")
+            if cid and val:
+                result[cid] = val[:10] if len(val) > 10 else val
+        return result
+
     @app.route("/api/channel-list")
     def channel_list():
         payload = {
@@ -1285,13 +1308,20 @@ def create_app(config: AppConfig = CONFIG) -> Flask:
             "source": str(config.channels_path),
         }
         try:
-            payload["channels"] = load_channel_entries(config.channels_path)
+            entries = load_channel_entries(config.channels_path)
         except FileNotFoundError:
             LOGGER.warning("Channel list not found: %s", config.channels_path)
             payload["error"] = "channels_not_found"
+            return jsonify(payload)
         except Exception as exc:
             LOGGER.exception("Failed to load channel list: %s", exc)
             payload["error"] = "channels_load_failed"
+            return jsonify(payload)
+
+        latest_dates = _channel_latest_dates()
+        for entry in entries:
+            entry["last_posted"] = latest_dates.get(entry.get("id")) or None
+        payload["channels"] = entries
         return jsonify(payload)
 
     @app.route("/channels.txt")