add Site context with social links editor and site-wide settings

- Add Site context for managing site-wide content (social links, nav items,
  announcement bar, footer content)
- Add SocialLink schema with URL normalization and platform auto-detection
  supporting 40+ platforms via host and 25+ via URI scheme
- Add NavItem schema for header/footer navigation (editor UI coming next)
- Add SiteEditor component with collapsible sections for each content type
- Wire social links card block and footer to use database data
- Filter empty URLs from display in shop components
- Add DetailsPreserver hook to preserve collapsible section state
- Add comprehensive tests for Site context and SocialLink functions
- Remove unused helper functions from onboarding to fix compiler warnings
- Move sync_edit_url_param helper to group handle_editor_event clauses

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

assets/js/app.js

@@ -679,7 +679,7 @@ const DirtyGuard = {
   }
 }
 
-// EditorSheet: handles click-outside, Escape, and mobile drag-to-resize
+// EditorSheet: handles click-outside, Escape, navigation guard, and mobile drag-to-resize
 const EditorSheet = {
   mounted() {
     // Close on Escape key
@@ -691,6 +691,37 @@ const EditorSheet = {
     }
     document.addEventListener("keydown", this._onKeydown)
 
+    // Navigation guard: warn on browser close/refresh
+    this._beforeUnload = (e) => {
+      if (this.el.dataset.dirty === "true") {
+        e.preventDefault()
+        e.returnValue = ""
+      }
+    }
+    window.addEventListener("beforeunload", this._beforeUnload)
+
+    // Navigation guard: intercept LiveView link clicks
+    this._clickGuard = (e) => {
+      if (this.el.dataset.dirty !== "true") return
+
+      const link = e.target.closest("a[data-phx-link]")
+      if (!link) return
+
+      // Don't block clicks inside the editor itself
+      if (this.el.contains(link)) return
+
+      // Block navigation and show custom modal
+      e.preventDefault()
+      e.stopImmediatePropagation()
+      this.pushEvent("editor_nav_blocked", { href: link.getAttribute("href") })
+    }
+    document.addEventListener("click", this._clickGuard, true)
+
+    // Handle navigation after save/discard
+    this.handleEvent("editor_navigate", ({ href }) => {
+      window.location.href = href
+    })
+
     // Restore saved height on mobile and mark as already opened
     this._restoreSavedHeight()
     this._hasDragged = !!localStorage.getItem("editor-panel-height")
@@ -712,6 +743,8 @@ const EditorSheet = {
 
   destroyed() {
     document.removeEventListener("keydown", this._onKeydown)
+    window.removeEventListener("beforeunload", this._beforeUnload)
+    document.removeEventListener("click", this._clickGuard, true)
     this._cleanupDragHandle()
   },
 
@@ -882,35 +915,33 @@ const Clipboard = {
   }
 }
 
-// DirtyGuard + Ctrl+Z / Ctrl+Shift+Z undo/redo for page editors
+// Preserve <details> open state across LiveView re-renders
+// Morphdom removes the open attribute when server doesn't send it,
+// so we store the state locally and restore it after each update.
+const DetailsPreserver = {
+  mounted() {
+    this._saveState()
+  },
+  beforeUpdate() {
+    this._saveState()
+  },
+  updated() {
+    this._restoreState()
+  },
+  _saveState() {
+    this._wasOpen = this.el.open
+  },
+  _restoreState() {
+    if (this._wasOpen !== undefined) {
+      this.el.open = this._wasOpen
+    }
+  }
+}
+
+// Ctrl+Z / Ctrl+Shift+Z undo/redo for page editors
+// Note: Navigation guards are now handled by EditorSheet hook
 const EditorKeyboard = {
   mounted() {
-    this._beforeUnload = (e) => {
-      if (this.el.dataset.dirty === "true") {
-        e.preventDefault()
-        e.returnValue = ""
-      }
-    }
-    window.addEventListener("beforeunload", this._beforeUnload)
-
-    // Intercept LiveView navigation clicks when editor has unsaved changes.
-    // Uses capture phase to fire before LiveView's own click handler.
-    this._clickGuard = (e) => {
-      if (this.el.dataset.dirty !== "true") return
-
-      const link = e.target.closest("a[data-phx-link]")
-      if (!link) return
-
-      // Don't block clicks inside the editor itself (e.g. block controls)
-      if (this.el.contains(link)) return
-
-      if (!window.confirm("You have unsaved changes that will be lost. Leave anyway?")) {
-        e.preventDefault()
-        e.stopImmediatePropagation()
-      }
-    }
-    document.addEventListener("click", this._clickGuard, true)
-
     const prefix = this.el.dataset.eventPrefix || ""
     this._keydown = (e) => {
       if ((e.ctrlKey || e.metaKey) && e.key === "z") {
@@ -926,8 +957,6 @@ const EditorKeyboard = {
   },
 
   destroyed() {
-    window.removeEventListener("beforeunload", this._beforeUnload)
-    document.removeEventListener("click", this._clickGuard, true)
     document.removeEventListener("keydown", this._keydown)
   }
 }
@@ -950,7 +979,7 @@ const Download = {
 const csrfToken = document.querySelector("meta[name='csrf-token']").getAttribute("content")
 const liveSocket = new LiveSocket("/live", Socket, {
   params: {_csrf_token: csrfToken, screen_width: window.innerWidth},
-  hooks: {...colocatedHooks, ColorSync, Lightbox, CartPersist, CartDrawer, ProductImageScroll, SearchModal, MobileNavDrawer, CollectionFilters, AnalyticsInit, AnalyticsExport, ChartTooltip, Clipboard, DirtyGuard, EditorKeyboard, EditorSheet, Download},
+  hooks: {...colocatedHooks, ColorSync, Lightbox, CartPersist, CartDrawer, ProductImageScroll, SearchModal, MobileNavDrawer, CollectionFilters, AnalyticsInit, AnalyticsExport, ChartTooltip, Clipboard, DetailsPreserver, DirtyGuard, EditorKeyboard, EditorSheet, Download},
 })
 
 // Show progress bar on live navigation and form submits