feat: auto-downgrading revision

[korolenkowork]

Closes #4665

📑 Description

This PR introduces automatic database downgrading support when rolling back KeepHQ to a previous version.

✅ Checks

• Main logic completed
• I have updated the documentation as required
• New logic covered by test
• E2E is written
• All the tests have passed

ℹ Additional Information

• From this commit onward, all migration files will be copied to the SECRET_MANAGER_DIRECTORY to enable safe database downgrades during rollback scenarios.
• A new environment variable ALLOW_DB_DOWNGRADE has been added to explicitly allow or prevent database downgrades, reducing the risk of accidental downgrades.

[vercel]

@EnotShow is attempting to deploy a commit to the KeepHQ Team on Vercel.

A member of the Team first needs to authorize it.

[shahargl]

hey @EnotShow - thanks for this PR!

as this PR introduces some major changes to how Keep works, I thought I would add some e2e tests for it (mainly install Keep, do some migration, then downgrade). wdyt?

[shahargl]

see comments

[codecov]

Codecov Report

Attention: Patch coverage is 8.45070% with 65 lines in your changes missing coverage. Please review.

Project coverage is 46.03%. Comparing base (1ae49bf) to head (f1328ef).
Report is 3 commits behind head on main.

Files with missing lines	Patch %	Lines
keep/api/core/db_on_start.py	8.45%	65 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4678      +/-   ##
==========================================
- Coverage   46.19%   46.03%   -0.16%     
==========================================
  Files         165      165              
  Lines       17495    17564      +69     
==========================================
+ Hits         8081     8086       +5     
- Misses       9414     9478      +64     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.

[shahargl]

see comments

[vercel]

Deployment failed with the following error:

The provided GitHub repository does not contain the requested branch or commit reference. Please ensure the repository is not empty.

[korolenkowork]

Hey @shahargl! Thx for your review! I made all the required changes, so it's ready for re-review :)

[shahargl]

@EnotShow let tests pass and if they will I'll review

[korolenkowork]

Hey @shahargl, it's resolved!

I also added a separate Docker Compose file for E2E migrations testing, which attaches a dedicated volume. Because it seems that accessing the same volume from different workflows was causing concurrent map writes, like this.