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/main.py

@@ -84,8 +84,8 @@ async def lifespan(app: FastAPI):
 
 
 app = FastAPI(
-    title=customer_config.get("platform_name", "天普零碳园区智慧能源管理平台"),
-    description=customer_config.get("platform_name_en", "Tianpu Zero-Carbon Park Smart Energy Management System"),
+    title=customer_config.get("platform_name", "Smart Energy Management Platform"),
+    description=customer_config.get("platform_name_en", "Smart Energy Management System"),
     version="1.0.0",
     lifespan=lifespan,
 )