feat(contact): add contact form with admin panel and navbar dropdown

Database changes:
- Added ContactMessage model to Prisma schema
- Fields: userId, username, firstName, lastName, email, subject, message, status, ipAddress
- Status enum: new, read, resolved
- Relation to User model

Backend changes:
- Added POST /api/public/contact endpoint for form submissions
- Works for both authenticated and non-authenticated users
- Validation for email, subject (3-255 chars), message (10-5000 chars)
- Activity logging for submissions
- Added admin endpoints:
  - GET /api/admin/contact-messages - list with filtering by status
  - GET /api/admin/contact-messages/:id - view single message (auto-marks as read)
  - PATCH /api/admin/contact-messages/:id/status - update status
  - DELETE /api/admin/contact-messages/:id - delete message

Frontend changes:
- Created ContactPage at /contact route
- For non-logged-in users: firstName, lastName, email, subject, message fields
- For logged-in users: auto-fills username, shows only email, subject, message
- Character counter for message (max 5000)
- Success screen with auto-redirect to homepage
- Created ContactMessagesPage at /admin/contact-messages
- Two-column layout: message list + detail view
- Filter by status (all, new, read, resolved)
- View message details with sender info and IP address
- Update status and delete messages
- Added admin dropdown menu to Navbar
  - Desktop: dropdown with Activity Logs and Contact Messages
  - Mobile: expandable submenu
  - Click outside to close on desktop
  - ChevronDown icon rotates when open

Note: CAPTCHA integration planned for future enhancement

backend/prisma/schema.prisma

@@ -77,6 +77,7 @@ model User {
   heats                   EventUserHeat[]
   recordingAssignments    RecordingSuggestion[] @relation("RecorderAssignments")
   activityLogs            ActivityLog[]
+  contactMessages         ContactMessage[]
 
   @@map("users")
 }
@@ -365,3 +366,37 @@ model ActivityLog {
 
   @@map("activity_logs")
 }
+
+// Contact messages from users
+model ContactMessage {
+  id        Int      @id @default(autoincrement())
+
+  // User identification (either logged in or anonymous)
+  userId    Int?     @map("user_id")        // NULL for non-logged-in users
+  username  String?  @db.VarChar(50)        // Username if logged in
+  firstName String?  @map("first_name") @db.VarChar(100) // For non-logged-in users
+  lastName  String?  @map("last_name") @db.VarChar(100)  // For non-logged-in users
+  email     String   @db.VarChar(255)       // Always required
+
+  // Message content
+  subject   String   @db.VarChar(255)
+  message   String   @db.Text
+
+  // Admin tracking
+  status    String   @default("new") @db.VarChar(20) // 'new', 'read', 'resolved'
+  ipAddress String?  @map("ip_address") @db.VarChar(45)
+
+  // Timestamps
+  createdAt DateTime @default(now()) @map("created_at")
+  updatedAt DateTime @updatedAt @map("updated_at")
+
+  // Relations
+  user      User?    @relation(fields: [userId], references: [id], onDelete: SetNull)
+
+  // Indexes
+  @@index([status, createdAt(sort: Desc)])
+  @@index([createdAt(sort: Desc)])
+  @@index([userId])
+
+  @@map("contact_messages")
+}