feat: add power plants layer with WRI Global Power Plant Database

Map ~35,000 power generation facilities from 164 countries using the
WRI Global Power Plant Database (CC BY 4.0). Follows the existing
datacenter layer pattern with clustered icon symbols, amber color
scheme, and click popups showing fuel type, capacity, and operator.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

backend/services/fetchers/_store.py

@@ -31,7 +31,8 @@ latest_data = {
     "internet_outages": [],
     "firms_fires": [],
     "datacenters": [],
-    "military_bases": []
+    "military_bases": [],
+    "power_plants": []
 }
 
 # Per-source freshness timestamps

backend/services/fetchers/infrastructure.py

@@ -180,6 +180,44 @@ def fetch_military_bases():
         _mark_fresh("military_bases")
 
 
+# ---------------------------------------------------------------------------
+# Power Plants (WRI Global Power Plant Database)
+# ---------------------------------------------------------------------------
+_POWER_PLANTS_PATH = Path(__file__).parent.parent.parent / "data" / "power_plants.json"
+
+
+def fetch_power_plants():
+    """Load WRI Global Power Plant Database (~35K facilities)."""
+    plants = []
+    try:
+        if not _POWER_PLANTS_PATH.exists():
+            logger.warning(f"Power plants file not found: {_POWER_PLANTS_PATH}")
+            return
+        raw = json.loads(_POWER_PLANTS_PATH.read_text(encoding="utf-8"))
+        for entry in raw:
+            lat = entry.get("lat")
+            lng = entry.get("lng")
+            if lat is None or lng is None:
+                continue
+            if not (-90 <= lat <= 90 and -180 <= lng <= 180):
+                continue
+            plants.append({
+                "name": entry.get("name", "Unknown"),
+                "country": entry.get("country", ""),
+                "fuel_type": entry.get("fuel_type", "Unknown"),
+                "capacity_mw": entry.get("capacity_mw"),
+                "owner": entry.get("owner", ""),
+                "lat": lat, "lng": lng,
+            })
+        logger.info(f"Power plants: {len(plants)} facilities loaded")
+    except Exception as e:
+        logger.error(f"Error loading power plants: {e}")
+    with _data_lock:
+        latest_data["power_plants"] = plants
+    if plants:
+        _mark_fresh("power_plants")
+
+
 # ---------------------------------------------------------------------------
 # CCTV Cameras
 # ---------------------------------------------------------------------------