feat(db): implement real migration status reporting

[GaspardKirira]

Summary

Implement migration status reporting for file-based migrations.

The current CLI accepts the status command but only prints the migrations directory and a placeholder message.

Current behavior

vix orm status reaches the DB migrator, but the migrator does not compare migration files with the migration tracking table.

Users cannot currently see:

• applied migrations;
• pending migrations;
• modified migrations;
• missing migration files;
• the last applied migration.

Expected behavior

The migration runner must expose enough information for the CLI to display the current migration state without modifying the database schema.

Scope

• Add an internal migration status representation.
• List discovered migration files.
• List applied migration records.
• Mark migrations as applied or pending.
• Detect checksum mismatches.
• Detect applied migrations whose files are missing.
• Display results through vix_db_migrator status.
• Return a non-zero status when migration history is inconsistent.
• Preserve the existing migration commands and public DB API.

Suggested files

• modules/db/include/vix/db/mig/FileMigrationsRunner.hpp
• modules/db/src/mig/FileMigrationsRunner.cpp
• modules/db/tools/migrator/MigratorCLI.cpp
• modules/db/tests/file_migrations_runner_test.cpp

Acceptance criteria

• Applied migrations are displayed.
• Pending migrations are displayed.
• Modified applied migrations are clearly identified.
• Missing applied migration files are clearly identified.
• Status does not apply or roll back migrations.
• Consistent migration history exits successfully.
• Inconsistent migration history exits with failure.
• Existing public DB usage remains compatible.

Non-goals

This issue does not include:

• an interactive migration UI;
• automatic repair of migration history;
• ORM migration status;
• migration generation.

Suggested labels

• scope:db
• type:feature
• good first issue
• status:ready