feat(subscriptions): migrate subscription management to merchant level and seed tiers

Move subscription create/edit from store detail (broken endpoint) to merchant
detail page with proper modal UI. Seed 4 subscription tiers (Essential,
Professional, Business, Enterprise) in init_production.py. Also includes
cross-module dependency declarations, store domain platform_id migration,
platform context middleware, CMS route fixes, and migration backups.

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

app/modules/tenancy/routes/api/admin_store_domains.py

@@ -78,6 +78,7 @@ def add_store_domain(
         is_active=domain.is_active,
         is_verified=domain.is_verified,
         ssl_status=domain.ssl_status,
+        platform_id=domain.platform_id,
         verification_token=domain.verification_token,
         verified_at=domain.verified_at,
         ssl_verified_at=domain.ssl_verified_at,
@@ -117,6 +118,7 @@ def list_store_domains(
                 is_active=d.is_active,
                 is_verified=d.is_verified,
                 ssl_status=d.ssl_status,
+                platform_id=d.platform_id,
                 verification_token=d.verification_token if not d.is_verified else None,
                 verified_at=d.verified_at,
                 ssl_verified_at=d.ssl_verified_at,
@@ -151,6 +153,7 @@ def get_domain_details(
         is_active=domain.is_active,
         is_verified=domain.is_verified,
         ssl_status=domain.ssl_status,
+        platform_id=domain.platform_id,
         verification_token=(
             domain.verification_token if not domain.is_verified else None
         ),
@@ -197,6 +200,7 @@ def update_store_domain(
         is_active=domain.is_active,
         is_verified=domain.is_verified,
         ssl_status=domain.ssl_status,
+        platform_id=domain.platform_id,
         verification_token=None,  # Don't expose token after updates
         verified_at=domain.verified_at,
         ssl_verified_at=domain.ssl_verified_at,