feat: consolidate media service, add merchant users page, fix metrics overlap

- Merge ImageService into MediaService with WebP variant generation,
  DB-backed storage stats, and module-driven media usage discovery
  via new MediaUsageProviderProtocol
- Add merchant users admin page with scoped user listing, stats
  endpoint, template, JS, and i18n strings (de/en/fr/lb)
- Fix merchant user metrics so Owners and Team Members are mutually
  exclusive (filter team_members on user_type="member" and exclude
  owner IDs) ensuring stat cards add up correctly
- Update billing and monitoring services to use media_service
- Update subscription-billing and feature-gating docs

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

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

@@ -38,6 +38,7 @@ def get_all_users(
     per_page: int = Query(10, ge=1, le=100),
     search: str = Query("", description="Search by username or email"),
     role: str = Query("", description="Filter by role"),
+    scope: str = Query("", description="Filter scope: 'merchant' for merchant owners and team members"),
     is_active: str = Query("", description="Filter by active status"),
     db: Session = Depends(get_db),
     current_admin: UserContext = Depends(get_current_admin_api),
@@ -54,11 +55,35 @@ def get_all_users(
         per_page=per_page,
         search=search if search else None,
         role=role if role else None,
+        scope=scope if scope else None,
         is_active=is_active_bool,
     )
 
+    if scope == "merchant":
+        items = [
+            UserDetailResponse(
+                id=user.id,
+                email=user.email,
+                username=user.username,
+                role=user.role,
+                is_active=user.is_active,
+                last_login=user.last_login,
+                created_at=user.created_at,
+                updated_at=user.updated_at,
+                first_name=user.first_name,
+                last_name=user.last_name,
+                full_name=user.full_name,
+                is_email_verified=user.is_email_verified,
+                owned_merchants_count=len(user.owned_merchants) if user.owned_merchants else 0,
+                store_memberships_count=len(user.store_memberships) if user.store_memberships else 0,
+            )
+            for user in users
+        ]
+    else:
+        items = [UserResponse.model_validate(user) for user in users]
+
     return UserListResponse(
-        items=[UserResponse.model_validate(user) for user in users],
+        items=items,
         total=total,
         page=page,
         per_page=per_page,
@@ -161,6 +186,42 @@ def get_user_statistics(
     return stats
 
 
+@admin_platform_users_router.get("/merchant-stats")
+def get_merchant_user_statistics(
+    request: Request,
+    db: Session = Depends(get_db),
+    current_admin: UserContext = Depends(get_current_admin_api),
+):
+    """Get merchant user statistics for admin dashboard.
+
+    Uses the stats_aggregator to get merchant user metrics from the tenancy
+    module's MetricsProvider.
+    """
+    platform_id = _get_platform_id(request, current_admin)
+
+    metrics = stats_aggregator.get_admin_dashboard_stats(db=db, platform_id=platform_id)
+    tenancy_metrics = metrics.get("tenancy", [])
+
+    stats = {
+        "merchant_users_total": 0,
+        "merchant_users_active": 0,
+        "merchant_owners": 0,
+        "merchant_team_members": 0,
+    }
+
+    for metric in tenancy_metrics:
+        if metric.key == "tenancy.merchant_users_total":
+            stats["merchant_users_total"] = int(metric.value)
+        elif metric.key == "tenancy.merchant_users_active":
+            stats["merchant_users_active"] = int(metric.value)
+        elif metric.key == "tenancy.merchant_owners":
+            stats["merchant_owners"] = int(metric.value)
+        elif metric.key == "tenancy.merchant_team_members":
+            stats["merchant_team_members"] = int(metric.value)
+
+    return stats
+
+
 @admin_platform_users_router.get("/search", response_model=UserSearchResponse)
 def search_users(
     q: str = Query(..., min_length=2, description="Search query (username or email)"),