P1: Fix sigortacudb.sql and add migrations

[Kinin-Code-Offical]

The sigortacudb.sql file has syntax errors and is not a reliable way to manage schema. A proper migration system must be established.

Acceptance Criteria:

• Fix all syntax errors in sigortacudb.sql.
• Introduce Phinx for database migrations.
• Create a phinx.php configuration file.
• Create an initial migration file in db/migrations/ that contains the entire corrected schema.
• The original sigortacudb.sql file should be considered deprecated.