feat: add dynamic meta tags for social sharing (Phase 4-5)

Phase 4: Dynamic Meta Tags
- Added react-helmet-async dependency
- Created SEOHead component with Open Graph and Twitter Card support
- Added HelmetProvider wrapper to App.tsx
- Integrated SEOHead in Product page (title, description, image, product info)
- Integrated SEOHead in Shop page (basic meta tags)

Phase 5: Auto-Flush Permalinks
- Enhanced settings change handler to only flush when spa_mode,
  spa_page, or use_browser_router changes
- Plugin already flushes on activation (Installer.php)

This enables proper link previews when sharing product URLs
on Facebook, Twitter, Slack, etc.

customer-spa/package-lock.json

@@ -28,6 +28,7 @@
                 "lucide-react": "^0.547.0",
                 "react": "^18.3.1",
                 "react-dom": "^18.3.1",
+                "react-helmet-async": "^2.0.5",
                 "react-hook-form": "^7.54.2",
                 "react-router-dom": "^7.9.4",
                 "sonner": "^2.0.7",
@@ -4927,6 +4928,15 @@
                 "node": ">= 0.4"
             }
         },
+        "node_modules/invariant": {
+            "version": "2.2.4",
+            "resolved": "https://registry.npmjs.org/invariant/-/invariant-2.2.4.tgz",
+            "integrity": "sha512-phJfQVBuaJM5raOpJjSfkiD6BpbCE4Ns//LaXl6wGYtUBY83nWS6Rf9tXm2e8VaK60JEjYldbPif/A2B1C2gNA==",
+            "license": "MIT",
+            "dependencies": {
+                "loose-envify": "^1.0.0"
+            }
+        },
         "node_modules/is-array-buffer": {
             "version": "3.0.5",
             "resolved": "https://registry.npmjs.org/is-array-buffer/-/is-array-buffer-3.0.5.tgz",
@@ -6214,6 +6224,26 @@
                 "react": "^18.3.1"
             }
         },
+        "node_modules/react-fast-compare": {
+            "version": "3.2.2",
+            "resolved": "https://registry.npmjs.org/react-fast-compare/-/react-fast-compare-3.2.2.tgz",
+            "integrity": "sha512-nsO+KSNgo1SbJqJEYRE9ERzo7YtYbou/OqjSQKxV7jcKox7+usiUVZOAC+XnDOABXggQTno0Y1CpVnuWEc1boQ==",
+            "license": "MIT"
+        },
+        "node_modules/react-helmet-async": {
+            "version": "2.0.5",
+            "resolved": "https://registry.npmjs.org/react-helmet-async/-/react-helmet-async-2.0.5.tgz",
+            "integrity": "sha512-rYUYHeus+i27MvFE+Jaa4WsyBKGkL6qVgbJvSBoX8mbsWoABJXdEO0bZyi0F6i+4f0NuIb8AvqPMj3iXFHkMwg==",
+            "license": "Apache-2.0",
+            "dependencies": {
+                "invariant": "^2.2.4",
+                "react-fast-compare": "^3.2.2",
+                "shallowequal": "^1.1.0"
+            },
+            "peerDependencies": {
+                "react": "^16.6.0 || ^17.0.0 || ^18.0.0"
+            }
+        },
         "node_modules/react-hook-form": {
             "version": "7.66.1",
             "resolved": "https://registry.npmjs.org/react-hook-form/-/react-hook-form-7.66.1.tgz",
@@ -6658,6 +6688,12 @@
                 "node": ">= 0.4"
             }
         },
+        "node_modules/shallowequal": {
+            "version": "1.1.0",
+            "resolved": "https://registry.npmjs.org/shallowequal/-/shallowequal-1.1.0.tgz",
+            "integrity": "sha512-y0m1JoUZSlPAjXVtPPW70aZWfIL/dSP7AFkRnniLCrK/8MDKog3TySTBmckD+RObVxH0v4Tox67+F14PdED2oQ==",
+            "license": "MIT"
+        },
         "node_modules/shebang-command": {
             "version": "2.0.0",
             "resolved": "https://registry.npmjs.org/shebang-command/-/shebang-command-2.0.0.tgz",