fix: add server name validation and clean invalid data before migration 009 (#591)

## Summary

This PR adds two important improvements to ensure data integrity:

1. **Adds server name format validation at the API layer** to match the
database constraint from migration 008
2. **Includes migration 008 to clean up invalid data** before applying
strict constraints in migration 009

## Changes

### Server Name Validation
- Enforces validation at the API layer matching the database constraint
- **Namespace pattern**: `[a-zA-Z0-9][a-zA-Z0-9.-]*[a-zA-Z0-9]` 
  - Must start and end with alphanumeric characters
  - Can contain dots and hyphens in the middle
- **Name pattern**: `[a-zA-Z0-9][a-zA-Z0-9._-]*[a-zA-Z0-9]`
  - Must start and end with alphanumeric characters  
  - Can contain dots, underscores, and hyphens in the middle
- Provides clear, user-friendly error messages indicating which part is
invalid
- Uses DRY approach with composed regex patterns

### Migration 008: Data Cleanup
- Removes servers with invalid names or empty versions (5 servers
affected in production)
- Fixes invalid status values by setting them to 'active' (1 server
affected)
- Removes duplicate name+version combinations
- Includes comprehensive safety checks to prevent accidental data loss
- Must run before migration 009 which adds strict constraints

## Testing
- All validator tests pass
- Migration includes safety checks that match production data
- CI verification included

---------

Co-authored-by: Claude <noreply@anthropic.com>

internal/validators/constants.go

@@ -28,6 +28,7 @@ var (
 
 	// Server name validation errors
 	ErrMultipleSlashesInServerName = errors.New("server name cannot contain multiple slashes")
+	ErrInvalidServerNameFormat     = errors.New("server name format is invalid")
 )
 
 // RepositorySource represents valid repository sources