Run full test suite in GitHub Actions with disposable test env

[devarshishimpi]

Description

Sets up CI to run the full Codra test suite on PRs, pushes to main, and manual workflow dispatches.

Changes include:

• Adds a Postgres service container for GitHub Actions test runs.
• Runs migrations before Vitest through npm test.
• Moves test env values out of test helpers and into env files / workflow env.
• Adds .env.test.example for local test setup.
• Updates .dev.vars.example to match the local .dev.vars env names.
• Removes DB test skipping so all 56 tests run locally and in CI.
• Trims CI env vars to only what the current tests actually require.
• Increases Vitest timeout for slower DB-backed integration tests.

Closes #1

Type of change

• New feature (non-breaking change which adds functionality)

How Has This Been Tested?

• Unit Tests
• Integration Tests
• Manual Dashboard Verification
• Manual GitHub Webhook Verification

Checklist:

• I have starred Codra on GitHub
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• My changes generate no new warnings
• New and existing unit tests pass locally with my changes
• I have signed the CLA