feat: platform-aware storefront routing and billing improvements

Overhaul storefront URL routing to be platform-aware:
- Dev: /platforms/{code}/storefront/{store_code}/
- Prod: subdomain.platform.lu/ (internally rewritten to /storefront/)
- Add subdomain detection in PlatformContextMiddleware
- Add /storefront/ path rewrite for prod mode (subdomain/custom domain)
- Remove all silent platform fallbacks (platform_id=1)
- Add require_platform dependency for clean endpoint validation
- Update route registration, templates, module definitions, base_url calc
- Update StoreContextMiddleware for /storefront/ path detection
- Remove /stores/ from FrontendDetector STOREFRONT_PATH_PREFIXES

Billing service improvements:
- Add store_platform_sync_service to keep store_platforms in sync
- Make tier lookups platform-aware across billing services
- Add tiers for all platforms in seed data
- Add demo subscriptions to seed

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

app/modules/core/routes/api/merchant_dashboard.py

@@ -14,7 +14,7 @@ import logging
 from fastapi import APIRouter, Depends, Request
 from sqlalchemy.orm import Session
 
-from app.api.deps import get_merchant_for_current_user
+from app.api.deps import get_merchant_for_current_user, require_platform
 from app.core.database import get_db
 from app.modules.core.schemas.dashboard import MerchantDashboardStatsResponse
 from app.modules.core.services.stats_aggregator import stats_aggregator
@@ -27,6 +27,7 @@ logger = logging.getLogger(__name__)
 def get_merchant_dashboard_stats(
     request: Request,
     merchant=Depends(get_merchant_for_current_user),
+    platform=Depends(require_platform),
     db: Session = Depends(get_db),
 ):
     """
@@ -41,8 +42,7 @@ def get_merchant_dashboard_stats(
     Merchant is resolved from the JWT token.
     Requires Authorization header (API endpoint).
     """
-    platform = getattr(request.state, "platform", None)
-    platform_id = platform.id if platform else 1
+    platform_id = platform.id
 
     flat = stats_aggregator.get_merchant_stats_flat(
         db=db,

app/modules/core/routes/api/store_dashboard.py

@@ -14,7 +14,7 @@ import logging
 from fastapi import APIRouter, Depends, Request
 from sqlalchemy.orm import Session
 
-from app.api.deps import get_current_store_api
+from app.api.deps import get_current_store_api, require_platform
 from app.core.database import get_db
 from app.modules.core.schemas.dashboard import (
     StoreCustomerStats,
@@ -49,6 +49,7 @@ def _extract_metric_value(
 def get_store_dashboard_stats(
     request: Request,
     current_user: UserContext = Depends(get_current_store_api),
+    platform=Depends(require_platform),
     db: Session = Depends(get_db),
 ):
     """
@@ -74,10 +75,7 @@ def get_store_dashboard_stats(
     if not store.is_active:
         raise StoreNotActiveException(store.store_code)
 
-    # Get aggregated metrics from all enabled modules
-    # Get platform_id from request context (set by PlatformContextMiddleware)
-    platform = getattr(request.state, "platform", None)
-    platform_id = platform.id if platform else 1
+    platform_id = platform.id
     metrics = stats_aggregator.get_store_dashboard_stats(
         db=db,
         store_id=store_id,