Migrate User Model ID from UUID to Integer

[avirajsingh7]

Summary

This PR replaces the UUID primary key in the User model with an auto-incrementing Integer ID. This change ensures consistency across the application, as most models and APIs rely on integer-based identifiers.

Target issue is #108

Key Changes

• Migrated user.id from UUID to INT using a dedicated mapping table (uuid_to_int_map) to preserve referential integrity.
• Updated all foreign key references to user.id in related tables (document, collection, projectuser, apikey) from UUID to INT.
• Added a new user_id_seq sequence to support auto-increment behavior for user.id.
• Re-established all dropped constraints and foreign keys.
• Ensured the migration maintains data integrity through controlled updates.

Affected Areas

• Database schema and Alembic migration logic.
• Any code depending on the User model’s ID type.
• Tests referencing user IDs.

Checklist

Before submitting a pull request, please ensure that you mark these task.

• Ran fastapi run --reload app/main.py or docker compose up in the repository root and test.
• If you've fixed a bug or added code that is tested and has test cases.

Notes

Please add here if any other information is required for the reviewer.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

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