fix: Improve database migration strategy - only migrate if needed

- Check if database exists before creating
- Only apply pending migrations
- Skip migration if database is up to date
- Prevents 'file already exists' error on restart

src/CMSMicroservice.Infrastructure/Persistence/ApplicationDbContextInitialiser.cs

@@ -23,7 +23,29 @@ public  class ApplicationDbContextInitialiser
         {
             if (_context.Database.IsSqlServer())
             {
-                await _context.Database.MigrateAsync();
+                // Check if database already exists and has pending migrations
+                bool dbExists = await _context.Database.CanConnectAsync();
+                
+                if (dbExists)
+                {
+                    _logger.LogInformation("Database exists, checking for pending migrations...");
+                    var pendingMigrations = await _context.Database.GetPendingMigrationsAsync();
+                    
+                    if (pendingMigrations.Any())
+                    {
+                        _logger.LogInformation("Applying {Count} pending migrations", pendingMigrations.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();
+                }
             }
         }
         catch (Exception ex)
@@ -32,7 +54,6 @@ public  class ApplicationDbContextInitialiser
             throw;
         }
     }
-
     public async Task SeedAsync()
     {
         try