feat: add PlatformSettings for pagination and vendor filter improvements

Platform Settings:
- Add PlatformSettings utility in init-alpine.js with 5-min cache
- Add Display tab in /admin/settings for rows_per_page config
- Integrate PlatformSettings.getRowsPerPage() in all paginated pages
- Standardize default per_page to 20 across all admin pages
- Add documentation at docs/frontend/shared/platform-settings.md

Architecture Rules:
- Add JS-010: enforce PlatformSettings usage for pagination
- Add JS-011: enforce standard pagination structure
- Add JS-012: detect double /api/v1 prefix in apiClient calls
- Implement all rules in validate_architecture.py

Vendor Filter (Tom Select):
- Add vendor filter to marketplace-products, vendor-products,
  customers, inventory, and vendor-themes pages
- Add selectedVendor display panel with clear button
- Add localStorage persistence for vendor selection
- Fix double /api/v1 prefix in vendor-selector.js

Bug Fixes:
- Remove duplicate PlatformSettings from utils.js
- Fix customers.js pagination structure (page_size → per_page)
- Fix code-quality-violations.js pagination structure

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

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

scripts/validate_architecture.py

@@ -2698,6 +2698,138 @@ class ArchitectureValidator:
             # JS-004: Check Alpine components set currentPage
             self._check_alpine_current_page(file_path, content, lines)
 
+            # JS-010: Check PlatformSettings usage for pagination
+            self._check_platform_settings_usage(file_path, content, lines)
+
+            # JS-011: Check standard pagination structure
+            self._check_pagination_structure(file_path, content, lines)
+
+            # JS-012: Check for double /api/v1 prefix in API calls
+            self._check_api_prefix_usage(file_path, content, lines)
+
+    def _check_platform_settings_usage(
+        self, file_path: Path, content: str, lines: list[str]
+    ):
+        """
+        JS-010: Check that pages with pagination use PlatformSettings.getRowsPerPage()
+        """
+        # Skip excluded files
+        excluded_files = ["init-alpine.js", "init-api-client.js", "settings.js"]
+        if file_path.name in excluded_files:
+            return
+
+        # Check if this file has pagination (look for pagination object)
+        has_pagination = re.search(r"pagination:\s*\{", content)
+        if not has_pagination:
+            return
+
+        # Check if file uses PlatformSettings
+        uses_platform_settings = "PlatformSettings" in content
+
+        if not uses_platform_settings:
+            # Find the line where pagination is defined
+            for i, line in enumerate(lines, 1):
+                if "pagination:" in line and "{" in line:
+                    self._add_violation(
+                        rule_id="JS-010",
+                        rule_name="Use PlatformSettings for pagination",
+                        severity=Severity.ERROR,
+                        file_path=file_path,
+                        line_number=i,
+                        message="Page with pagination must use PlatformSettings.getRowsPerPage()",
+                        context=line.strip()[:80],
+                        suggestion="Add: if (window.PlatformSettings) { this.pagination.per_page = await window.PlatformSettings.getRowsPerPage(); }",
+                    )
+                    break
+
+    def _check_pagination_structure(
+        self, file_path: Path, content: str, lines: list[str]
+    ):
+        """
+        JS-011: Check that pagination uses standard structure (pagination.per_page not page_size)
+        """
+        # Skip excluded files
+        excluded_files = ["init-alpine.js"]
+        if file_path.name in excluded_files:
+            return
+
+        # Check if this file has pagination
+        has_pagination = re.search(r"pagination:\s*\{", content)
+        if not has_pagination:
+            return
+
+        # Check for wrong property names in pagination object definition
+        # Look for pagination object with wrong property names
+        wrong_patterns = [
+            (r"page_size\s*:", "page_size", "per_page"),
+            (r"pageSize\s*:", "pageSize", "per_page"),
+            (r"total_pages\s*:", "total_pages", "pages"),
+            (r"totalPages\s*:", "totalPages (in pagination object)", "pages"),
+        ]
+
+        # Find the pagination object definition and check its properties
+        in_pagination_block = False
+        brace_count = 0
+
+        for i, line in enumerate(lines, 1):
+            # Detect start of pagination object
+            if "pagination:" in line and "{" in line:
+                in_pagination_block = True
+                brace_count = line.count("{") - line.count("}")
+                continue
+
+            if in_pagination_block:
+                brace_count += line.count("{") - line.count("}")
+
+                # Check for wrong property names only inside the pagination block
+                for pattern, wrong_name, correct_name in wrong_patterns:
+                    if re.search(pattern, line):
+                        self._add_violation(
+                            rule_id="JS-011",
+                            rule_name="Use standard pagination structure",
+                            severity=Severity.ERROR,
+                            file_path=file_path,
+                            line_number=i,
+                            message=f"Use '{correct_name}' instead of '{wrong_name}' in pagination",
+                            context=line.strip()[:80],
+                            suggestion=f"Rename '{wrong_name}' to '{correct_name}'",
+                        )
+
+                # Exit pagination block when braces close
+                if brace_count <= 0:
+                    in_pagination_block = False
+
+    def _check_api_prefix_usage(
+        self, file_path: Path, content: str, lines: list[str]
+    ):
+        """
+        JS-012: Check that apiClient calls don't include /api/v1 prefix
+        (apiClient adds this prefix automatically)
+        """
+        # Skip excluded files
+        excluded_files = ["init-api-client.js", "api-client.js"]
+        if file_path.name in excluded_files:
+            return
+
+        for i, line in enumerate(lines, 1):
+            # Skip comments
+            stripped = line.strip()
+            if stripped.startswith("//") or stripped.startswith("*"):
+                continue
+
+            # Check for apiClient calls with /api/v1 prefix
+            if re.search(r"apiClient\.(get|post|put|delete|patch)\s*\(\s*['\"`]/api/v1", line):
+                self._add_violation(
+                    rule_id="JS-012",
+                    rule_name="Do not include /api/v1 prefix",
+                    severity=Severity.ERROR,
+                    file_path=file_path,
+                    line_number=i,
+                    message="apiClient already adds /api/v1 prefix - remove it from the endpoint",
+                    context=line.strip()[:80],
+                    suggestion="Change '/api/v1/admin/...' to '/admin/...'",
+                )
+
     def _validate_templates(self, target_path: Path):
         """Validate template patterns"""
         print("📄 Validating templates...")