feat(schema): Implement multi-table validation for schema command

[litedatum]

** This issue focuses on enhancing the schema command to support validating multiple database tables from a single data source in one run. This is a key feature
for improving the tool's utility in complex environments.

Depends on: Completion of Issue #1 (CLI Refactoring).

Acceptance Criteria:

• The schema command is updated to use the new --conn option. It should not require a --table option, as the target tables will be defined within the rules
  file.
• The command can successfully parse a new multi-table --rules file format, where the top-level JSON is an object with table names as keys.
• The CLI's rule decomposition logic is updated to iterate through each table defined in the rules file and generate a complete list of atomic rules for the
  core engine.
• The command's output is clearly grouped by table name to make results easy to interpret.
• New unit and integration tests are added to cover multi-table validation scenarios.
  **

Resolve #27