fix: normalize dev versions to valid SemVer strings

[SatyamPandey-07]

Summary

• Headline: Normalize development and fallback build version strings to valid SemVer 2.0 identifiers.
• Motivation: When running tests or starting Kolibri in environments without release tags (e.g. fresh clones, forks, or shallow checkouts), setuptools-scm emits fallback development versions such as 0.1.dev38363+g356cfe2f5. During module initialization, kolibri.core.upgrade passes kolibri.__version__ through normalize_version_to_semver() before parsing it with semver.VersionInfo.parse(). Due to a regex flaw in normalize_version_to_semver(), the preceding dot before .dev was captured into the numeric prefix and .dev was duplicated into both after and dev, producing 0.1.-dev38363.dev38363.g356cfe2f5. This causes semver.VersionInfo.parse() to raise an unhandled ValueError: ... is not valid SemVer string, breaking pytest and Django startup entirely. Similarly, standard post-release dev strings like 0.1.2.dev6+gdef09150 resulted in 0.1.2-dev6.dev6.gdef09150.
• Approach:
  1. Deconstruct the version string into its pre-dev base and .dev suffix separately so the dev fragment is never matched twice.
  2. Parse the base version using ^\d+\.\d+(?:\.\d+)? to prevent trailing dot leakage into the numeric prefix.
  3. Ensure bipartite numeric versions followed by a dev suffix (e.g., 0.1.dev...) receive a .0 patch segment so they comply with SemVer's MAJOR.MINOR.PATCH specification.
  4. Preserve existing behavior for standard release and prerelease tags (0.15.0, 1.10, 0.14a1, 0.16b1).
  5. Add unit test coverage in kolibri/utils/tests/test_version.py for both setuptools-scm dev and bipartite fallback versions.

References

• Fixes [Brief description] Fix invalid SemVer normalization for development and setuptools-scm version strings #15269

Reviewer guidance

• Run unit tests for version normalization:

  uv run pytest kolibri/utils/tests/test_version.py

  All 76 tests should pass.
• Verify Django test settings load and execute properly on dev builds:

  uv run pytest kolibri/core/courses/test/test_models.py

  Verify that kolibri.core.upgrade imports cleanly without ValueError.
• Verify code formatting and linting:

  uv run ruff check kolibri/utils/version.py kolibri/utils/tests/test_version.py
  uv run ruff format --check kolibri/utils/version.py kolibri/utils/tests/test_version.py

AI usage

I used Antigravity / Gemini to locate where kolibri.core.upgrade fails during pytest startup and identify the regex mismatch in normalize_version_to_semver(). I reviewed the SemVer 2.0 specification and semver library constraints, implemented the fix to prevent trailing dot leakage and duplicate .dev fragments, wrote regression tests in kolibri/utils/tests/test_version.py, and verified the entire test suite runs without errors.

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[SatyamPandey-07]

@AlexVelezLl just bumping this PR in case it slipped through your notifications. Let me know if you need any changes or further testing!

[SatyamPandey-07]

@rtibbles just bumping this PR in case it slipped through your notifications. Let me know if you need any changes or further testing!