fix: Use EnsureCreatedAsync instead of MigrateAsync for initial db setup

- EnsureCreatedAsync creates db only if it doesn't exist
- Returns false if db already exists (idempotent)
- Prevents 'CMS.mdf already exists' error
- Still applies pending migrations when needed

src/CMSMicroservice.Infrastructure/Persistence/ApplicationDbContextInitialiser.cs

@@ -23,28 +23,24 @@ public  class ApplicationDbContextInitialiser
         {
             if (_context.Database.IsSqlServer())
             {
-                // Check if database already exists and has pending migrations
-                bool dbExists = await _context.Database.CanConnectAsync();
+                // Use EnsureCreated for initial setup, then apply migrations
+                // EnsureCreated is idempotent - safe to call multiple times
+                var created = await _context.Database.EnsureCreatedAsync();
                 
-                if (dbExists)
+                if (!created)
                 {
-                    _logger.LogInformation("Database exists, checking for pending migrations...");
-                    var pendingMigrations = await _context.Database.GetPendingMigrationsAsync();
-                    
-                    if (pendingMigrations.Any())
+                    // Database exists, check for pending migrations
+                    _logger.LogInformation("Database already exists, checking for migrations...");
+                    var pending = await _context.Database.GetPendingMigrationsAsync();
+                    if (pending.Any())
                     {
-                        _logger.LogInformation("Applying {Count} pending migrations", pendingMigrations.Count());
+                        _logger.LogInformation("Applying {Count} pending migrations", pending.Count());
                         await _context.Database.MigrateAsync();
                     }
-                    else
-                    {
-                        _logger.LogInformation("Database is up to date, no migrations needed");
-                    }
                 }
                 else
                 {
-                    _logger.LogInformation("Database does not exist, creating and migrating...");
-                    await _context.Database.MigrateAsync();
+                    _logger.LogInformation("Database created successfully");
                 }
             }
         }