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/services/alarm_checker.py

@@ -104,7 +104,7 @@ async def _send_alarm_email(
         platform_url=settings.PLATFORM_URL,
     )
 
-    subject = f"[{severity_cfg['label']}] {event.title} - 天普EMS告警通知"
+    subject = f"[{severity_cfg['label']}] {event.title} - EMS Alarm Notification"
     asyncio.create_task(send_email(to=emails, subject=subject, body_html=body_html))
 
 # Rate limit: don't create duplicate events for the same rule+device within this window