feat: rich text editor, image crop component, empty DB resilience

- RichTextarea with toolbar (Bold, Italic, List, Heading) + Ctrl+B/I
  hotkeys (layout-independent), active state highlighting, preview mode
- Shared ImageCropField component (replaces duplicate in news/classes)
  with drag-to-reposition, Ctrl+scroll zoom, compact layout
- SectionEditor defaultData prop — all admin pages handle empty DB
- Team: section title editable, toast notifications, unsaved data warning
  on navigation (back button, sidebar links, browser close)
- Carousel: continuous card wrapping during drag, edge fade for small teams
- Markup renderer: **bold**, *italic*, ## headings, 🤍 bullet points
- Empty DB guards on all public site sections
- Fix: upload error handling, contact phone field, "team" section key

src/app/admin/contact/page.tsx

@@ -28,7 +28,7 @@ function PhoneField({ value, onChange }: { value: string; onChange: (v: string)
     onChange(formatted);
   }
 
-  const digits = value.replace(/\D/g, "");
+  const digits = (value ?? "").replace(/\D/g, "");
   const isComplete = digits.length === 12;
 
   return (
@@ -163,7 +163,7 @@ function AddressList({ items, onChange }: { items: string[]; onChange: (items: s
 
 export default function ContactEditorPage() {
   return (
-    <SectionEditor<ContactInfo> sectionKey="contact" title="Контакты">
+    <SectionEditor<ContactInfo> sectionKey="contact" title="Контакты" defaultData={{ addresses: [] }}>
       {(data, update) => (
         <div className="space-y-4">
           <InputField