feat: multi-customer architecture + Z-Park support + Gitea migration scripts

Multi-customer config system:
- CUSTOMER env var selects customer (tianpu/zpark)
- customers/tianpu/config.yaml — Tianpu branding, collectors, features
- customers/zpark/config.yaml — Z-Park branding, Sungrow collector
- GET /api/v1/branding endpoint for customer-specific branding
- main.py loads customer config for app title, CORS, logging
- Collector manager filters by customer's enabled collectors

Z-Park (中关村医疗器械园) support:
- Sungrow iSolarCloud API collector (sungrow_collector.py)
- Z-Park device definitions (10 inverters, 8 combiner boxes, 22+ buildings)
- Z-Park TOU pricing config (Beijing 2026 rates)
- Z-Park seed script (seed_zpark.py)

Gitea migration scripts (Mac Studio → labmac3):
- 5 migration scripts + README in scripts/gitea-migration/
- Creates 3-repo structure: ems-core, tp-ems, zpark-ems

Version: v1.0.0

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

backend/app/api/v1/branding.py

@@ -0,0 +1,20 @@
+from fastapi import APIRouter
+from app.core.config import get_settings
+
+router = APIRouter(prefix="/branding", tags=["品牌配置"])
+
+
+@router.get("")
+async def get_branding():
+    """Return customer-specific branding configuration"""
+    settings = get_settings()
+    customer_config = settings.load_customer_config()
+    return {
+        "customer": settings.CUSTOMER,
+        "customer_name": customer_config.get("customer_name", settings.CUSTOMER),
+        "platform_name": customer_config.get("platform_name", settings.APP_NAME),
+        "platform_name_en": customer_config.get("platform_name_en", "Smart EMS"),
+        "logo_url": customer_config.get("logo_url", ""),
+        "theme_color": customer_config.get("theme_color", "#1890ff"),
+        "features": customer_config.get("features", {}),
+    }