test : add unit tests for cv-classifier.ts #3029

Summary of What Needs to be Done: Add comprehensive unit tests for src/lib/cv/cv-classifier.ts. The module explicitly states that every function is pure with no network calls, database access, or shared state mutations. The following functions need tests: detectTechnologies, mapToDomains, scoreContributions, analyzeRepository, classifyContributions, and filterByRole.

Changes that Need to be Made:

• Create test/cv-classifier.test.ts with Vitest
• Test detectTechnologies: provide minimal RepositoryData arrays, verify languages are bucketed into languages/frameworks/tools correctly; verify duplicate tech items are summed; verify sorting by occurrences descending
• Test mapToDomains: verify scores are computed correctly for Frontend/Backend domains when matching technologies are present; verify keyword bonus; verify FullStack synthetic domain is added when both Frontend and Backend scores exceed 30
• Test scoreContributions: verify totals are summed correctly from repository data; verify avgPRSize is computed correctly; verify topLanguages are sorted by frequency
• Test analyzeRepository: verify complexity classification (low/medium/high) based on lines changed and PR count; verify detectedDomains are populated correctly; verify relevanceByRole scores
• Test classifyContributions: verify it produces a valid ContributionClassification object with all required fields
• Test filterByRole: verify filtering by Frontend Developer removes non-Frontend technologies and repos with 0 relevance; verify repos are sorted by relevance descending

Impact that it would Provide: The CV classifier is a critical piece of the AI resume generation pipeline. Since it operates entirely on in-memory data (no external calls), tests are fast and deterministic. Coverage here prevents regression in contribution classification logic as the feature evolves.

Hello @Priyanshu-byte-coder, please assign this issue to me (@tmdeveloper007) so I can open a focused PR.