feat: add configurable currency locale and fix vendor JS init

Currency Locale Configuration:
- Add platform-level storefront settings (locale, currency)
- Create PlatformSettingsService with resolution chain:
  vendor → AdminSetting → environment → hardcoded fallback
- Add storefront_locale nullable field to Vendor model
- Update shop routes to resolve and pass locale to templates
- Add window.SHOP_CONFIG for frontend JavaScript access
- Centralize formatPrice() in shop-layout.js using SHOP_CONFIG
- Remove local formatPrice functions from shop templates

Vendor JS Bug Fix:
- Fix vendorCode being null on all vendor pages
- Root cause: page components overriding init() without calling parent
- Add parent init call to 14 vendor JS files
- Add JS-013 architecture rule to prevent future regressions
- Validator now checks vendor JS files for parent init pattern

Files changed:
- New: app/services/platform_settings_service.py
- New: alembic/versions/s7a8b9c0d1e2_add_storefront_locale_to_vendors.py
- Modified: 14 vendor JS files, shop templates, validation scripts

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

scripts/validate_architecture.py

@@ -2862,6 +2862,9 @@ class ArchitectureValidator:
             # JS-012: Check for double /api/v1 prefix in API calls
             self._check_api_prefix_usage(file_path, content, lines)
 
+            # JS-013: Check that components overriding init() call parent init
+            self._check_parent_init_call(file_path, content, lines)
+
     def _check_platform_settings_usage(
         self, file_path: Path, content: str, lines: list[str]
     ):
@@ -2995,6 +2998,59 @@ class ArchitectureValidator:
                     suggestion="Change '/api/v1/admin/...' to '/admin/...'",
                 )
 
+    def _check_parent_init_call(
+        self, file_path: Path, content: str, lines: list[str]
+    ):
+        """
+        JS-013: Check that vendor components overriding init() call parent init.
+
+        When a component uses ...data() to inherit base layout functionality AND
+        defines its own init() method, it MUST call the parent init first to set
+        critical properties like vendorCode.
+
+        Note: This only applies to vendor JS files because the vendor data() has
+        an init() method that extracts vendorCode from URL. Admin data() does not.
+        """
+        # Only check vendor JS files (admin data() doesn't have init())
+        if "/vendor/js/" not in str(file_path):
+            return
+
+        # Skip files that shouldn't have this pattern
+        excluded_files = ["init-alpine.js", "login.js", "onboarding.js"]
+        if file_path.name in excluded_files:
+            return
+
+        # Check if file uses ...data() spread operator
+        uses_data_spread = "...data()" in content
+
+        # Check if file defines its own async init()
+        has_own_init = re.search(r"async\s+init\s*\(\s*\)", content)
+
+        # If both conditions are true, check for parent init call
+        if uses_data_spread and has_own_init:
+            # Check for parent init call patterns
+            calls_parent_init = (
+                "data().init" in content
+                or "parentInit" in content
+                or "parent.init" in content
+            )
+
+            if not calls_parent_init:
+                # Find the line with async init() to report
+                for i, line in enumerate(lines, 1):
+                    if re.search(r"async\s+init\s*\(\s*\)", line):
+                        self._add_violation(
+                            rule_id="JS-013",
+                            rule_name="Components overriding init() must call parent init",
+                            severity=Severity.ERROR,
+                            file_path=file_path,
+                            line_number=i,
+                            message="Component with ...data() must call parent init() to set vendorCode",
+                            context=line.strip()[:80],
+                            suggestion="Add: const parentInit = data().init; if (parentInit) { await parentInit.call(this); }",
+                        )
+                        break
+
     def _validate_templates(self, target_path: Path):
         """Validate template patterns"""
         print("📄 Validating templates...")