fix: validate catalog entity names to reject empty, control chars, and overlength

[zfarrell]

Summary

• Add validate_name() function that rejects empty/whitespace-only names, ASCII control characters, and names exceeding 1024 characters
• Validate column names in ColumnDef::new() and ColumnDef::from_arrow()
• Validate schema and table names in SqliteMetadataWriter (get_or_create_schema, get_or_create_table, begin_write_transaction)
• Integrate with existing validate_table_name() to share validation logic

Test plan

• Unit tests for validate_name() with valid names, empty, whitespace, control chars, length limits
• Tests for ColumnDef rejecting empty and control-char names via both constructors
• Integration tests for SqliteMetadataWriter rejecting invalid schema/table names
• cargo test passes