feat: draft mode, admin branding, and workflow improvements

Draft Mode:
- Events are created as drafts by default — no email sent until published
- Add "Publish & Notify Client" button with confirmation dialog
- Draft banner with yellow styling on event details page
- Draft filter tab in events list
- Gallery middleware blocks public access to draft events
- Migration 076 adds is_draft column to events table

Admin Draft Preview:
- Admins can preview draft galleries via JWT preview token (?preview=)
- "View Gallery" link on drafts auto-appends preview token

Admin & Login Page Branding:
- Admin header uses configured company logo/name from branding settings
- Login page shows configured logo instead of hardcoded PicPeak
- Respects logo_display_mode (logo_only, text_only, logo_and_text)

OG Tag Branding:
- DynamicFavicon component updates OG meta tags and page title from
  branding settings

Editable Client Email:
- Customer email is now editable after event creation in edit mode

Branding Inheritance:
- New events inherit hero logo settings (visibility, size, position)
  from global branding configuration

Share Link Full Domain URL:
- New getFrontendBaseUrl() utility with DB fallback to general_site_url
- Used in email processor and share link service

frontend/src/components/common/DynamicFavicon.tsx

@@ -40,7 +40,7 @@ export const DynamicFavicon: React.FC = () => {
     }
   }, [settings?.branding_favicon_url]);
 
-  // Update document title when company name or tagline changes
+  // Update document title and OG meta tags when company name or tagline changes
   useEffect(() => {
     const companyName = settings?.branding_company_name?.trim();
     const tagline = settings?.branding_company_tagline?.trim();
@@ -52,6 +52,33 @@ export const DynamicFavicon: React.FC = () => {
     } else {
       document.title = DEFAULT_TITLE;
     }
+
+    // Update OG meta tags
+    const title = companyName || 'PicPeak';
+    const description = tagline || 'Photo Sharing Platform';
+
+    const updateMeta = (property: string, content: string) => {
+      let meta = document.querySelector(`meta[property="${property}"]`) as HTMLMetaElement | null;
+      if (!meta) {
+        meta = document.createElement('meta');
+        meta.setAttribute('property', property);
+        document.head.appendChild(meta);
+      }
+      meta.content = content;
+    };
+
+    updateMeta('og:title', document.title);
+    updateMeta('og:site_name', title);
+    updateMeta('og:description', description);
+
+    // Also update standard meta description
+    let metaDesc = document.querySelector('meta[name="description"]') as HTMLMetaElement | null;
+    if (!metaDesc) {
+      metaDesc = document.createElement('meta');
+      metaDesc.name = 'description';
+      document.head.appendChild(metaDesc);
+    }
+    metaDesc.content = description;
   }, [settings?.branding_company_name, settings?.branding_company_tagline]);
 
   return null;