feat(analytics): scope quality/review/evolution/generation data to selected project source

[mrveiss]

Context

#3436 added source_id validation to the 4 analytics API modules — if the source ID is unknown the endpoint returns 404. However the actual query/data returned is still global (not filtered to the selected project's repo path).

The backend docstrings currently say "scope results to a project" which overstates the current behaviour. Phase 1 was intentionally scoped to wiring + validation only.

What needs to happen (Phase 2)

For each module, use the resolved source_root path to scope analysis:

• analytics_quality.py — pass source_root to the quality scorer so metrics reflect that project's files only
• analytics_code_review.py — restrict pattern scan to files under source_root
• analytics_evolution.py — scope Redis evolution: key prefix to evolution:{source_id}: so snapshots are stored and retrieved per-project
• analytics_code_generation.py — restrict generation context to files under source_root

Also update the docstrings in each module to accurately reflect what source_id does after this change.

[mrveiss]

✅ Resolved in PR #3705 — analytics data scoped to project source_root.