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/templates/alarm_email.html

@@ -13,8 +13,8 @@
   <!-- Header -->
   <tr>
     <td style="background: linear-gradient(135deg, #1a73e8, #0d47a1); padding:24px 32px; text-align:center;">
-      <div style="font-size:12px; color:rgba(255,255,255,0.8); margin-bottom:4px;">TIANPU EMS</div>
-      <div style="font-size:20px; font-weight:bold; color:#ffffff; letter-spacing:1px;">天普零碳园区智慧能源管理平台</div>
+      <div style="font-size:12px; color:rgba(255,255,255,0.8); margin-bottom:4px;">EMS PLATFORM</div>
+      <div style="font-size:20px; font-weight:bold; color:#ffffff; letter-spacing:1px;">Smart Energy Management Platform</div>
     </td>
   </tr>
 
@@ -85,7 +85,7 @@
     <td style="background-color:#f8f9fa; padding:16px 32px; border-top:1px solid #e8e8e8;">
       <div style="font-size:12px; color:#999; text-align:center; line-height:1.6;">
         此为系统自动发送，请勿回复。<br>
-        天普零碳园区智慧能源管理平台 &copy; 2026
+        Smart Energy Management Platform &copy; 2026
       </div>
     </td>
   </tr>