feat: Add admin calendar and improve availability management

- Add admin calendar component with booking overview and status management
- Implement treatment-specific availability slots with automatic duration
- Enhance availability management with better UI and error handling
- Move admin credentials to .env configuration
- Add .env.example with all required environment variables
- Update README.md with comprehensive setup guide including PowerShell password hash generation
- Improve slot deletion with proper error handling and user feedback
- Add toast notifications for better UX

src/server/rpc/auth.ts

@@ -34,20 +34,31 @@ const verifyPassword = (password: string, hash: string): boolean => {
   return hashPassword(password) === hash;
 };
 
+// Export hashPassword for external use (e.g., generating hashes for .env)
+export const generatePasswordHash = hashPassword;
+
 // Initialize default owner account
 const initializeOwner = async () => {
   const existingUsers = await usersKV.getAllItems();
   if (existingUsers.length === 0) {
     const ownerId = randomUUID();
+    
+    // Get admin credentials from environment variables
+    const adminUsername = process.env.ADMIN_USERNAME || "owner";
+    const adminPasswordHash = process.env.ADMIN_PASSWORD_HASH || hashPassword("admin123");
+    const adminEmail = process.env.ADMIN_EMAIL || "owner@stargirlnails.de";
+    
     const owner: User = {
       id: ownerId,
-      username: "owner",
-      email: "owner@stargirlnails.de",
-      passwordHash: hashPassword("admin123"), // Default password
+      username: adminUsername,
+      email: adminEmail,
+      passwordHash: adminPasswordHash,
       role: "owner",
       createdAt: new Date().toISOString(),
     };
     await usersKV.setItem(ownerId, owner);
+    
+    console.log(`✅ Admin account created: username="${adminUsername}", email="${adminEmail}"`);
   }
 };