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/alembic/versions/002_add_system_settings.py

@@ -26,7 +26,7 @@ def upgrade() -> None:
     # Seed default settings
     op.execute("""
         INSERT INTO system_settings (key, value, description) VALUES
-        ('platform_name', '天普零碳园区智慧能源管理平台', '平台名称'),
+        ('platform_name', 'Smart Energy Management Platform', '平台名称'),
         ('data_retention_days', '365', '数据保留天数'),
         ('alarm_auto_resolve_minutes', '30', '告警自动解除时间(分钟)'),
         ('simulator_interval_seconds', '15', '模拟器采集间隔(秒)'),