feat!: generic defaults, dashboard fallback, PV filter fix (v1.3.0)

- Replace all hardcoded Tianpu/天普 defaults with generic "EMS Platform"
- Add energy_today fallback: query raw energy_data when daily summary empty
- Fix PV device filter to include sungrow_inverter device type
- Update APP_NAME, CUSTOMER default, SECRET_KEY, SMTP, Celery, email templates

BREAKING: CUSTOMER default changed from "tianpu" to "default"
Existing deployments with CUSTOMER=tianpu in .env are unaffected.

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

backend/app/api/v1/settings.py

@@ -12,7 +12,7 @@ router = APIRouter(prefix="/settings", tags=["系统设置"])
 
 # Default settings — used when keys are missing from DB
 DEFAULTS: dict[str, str] = {
-    "platform_name": "天普零碳园区智慧能源管理平台",
+    "platform_name": "Smart Energy Management Platform",
     "data_retention_days": "365",
     "alarm_auto_resolve_minutes": "30",
     "simulator_interval_seconds": "15",