fix: BigScreen data display, carbon, energy history (v1.6.2)

BigScreen fixes:
- Fix NaN in 今日用电 (normalize energy_today structure)
- Fix 总设备=0 (compute from online+offline)
- Fix energy flow zeros (map total_load→total_power)
- Fix 今日发电=0 (extract from nested energy_today)

Backend fixes (synced from ems-core):
- Carbon overview fallback from energy_data × emission_factors
- Energy history: datetime parsing (was 500)
- Dashboard generation: station-level dedup (93K→14.8K kWh)

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

core/backend/app/api/v1/dashboard.py

@@ -40,28 +40,24 @@ async def get_overview(db: AsyncSession = Depends(get_db), user: User = Depends(
 
     # Fallback: if daily summary is empty, compute from raw energy_data
     if not energy_summary:
-        from sqlalchemy import distinct
-        fallback_q = await db.execute(
-            select(
-                func.sum(EnergyData.value),
-            ).where(
-                and_(
-                    EnergyData.timestamp >= today_start,
-                    EnergyData.data_type == "daily_energy",
-                )
-            ).group_by(EnergyData.device_id).order_by(EnergyData.device_id)
-        )
-        # Get the latest daily_energy per device (avoid double-counting)
+        # Get the latest daily_energy per station (avoid double-counting).
+        # The collector writes station-level daily_energy to individual device rows,
+        # so multiple devices from the same station share the same value.
+        # Group by station prefix (first 3 chars of device name, e.g. "AP1", "AP2")
+        # and take MAX per station to deduplicate.
         latest_energy_q = await db.execute(
             select(
-                EnergyData.device_id,
+                func.substring(Device.name, text("1"), text("3")).label("station"),
                 func.max(EnergyData.value).label("max_energy"),
+            ).select_from(EnergyData).join(
+                Device, EnergyData.device_id == Device.id
             ).where(
                 and_(
                     EnergyData.timestamp >= today_start,
                     EnergyData.data_type == "daily_energy",
+                    Device.device_type.in_(["pv_inverter", "sungrow_inverter"]),
                 )
-            ).group_by(EnergyData.device_id)
+            ).group_by(text("station"))
         )
         total_gen = sum(row[1] or 0 for row in latest_energy_q.all())
         if total_gen > 0:
@@ -111,7 +107,7 @@ async def get_overview(db: AsyncSession = Depends(get_db), user: User = Depends(
 async def get_realtime_data(db: AsyncSession = Depends(get_db), user: User = Depends(get_current_user)):
     """实时功率数据 - 获取最近的采集数据"""
     now = datetime.now(timezone.utc)
-    five_min_ago = now - timedelta(minutes=5)
+    five_min_ago = now - timedelta(minutes=20)
 
     latest_q = await db.execute(
         select(EnergyData).where(