fix: sanitize URL path before database lookup

[aaniya22]

Summary

Fixes parseRepoParam in repo-analytics-utils.ts to normalise leading and consecutive slashes in "owner/repo" input before validating, instead of silently returning null for inputs like /owner/repo or owner//repo.

Closes #3032

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Type of Change

• 🐛 Bug fix (non-breaking change that fixes an issue)
• ✨ New feature (non-breaking change that adds functionality)
• 💥 Breaking change (fix or feature that changes existing behavior)
• 📝 Documentation update
• ♻️ Refactor / code cleanup (no functional change)
• ⚡ Performance improvement
• 🔒 Security fix
• 🧪 Tests only

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What Changed

• src/lib/repo-analytics-utils.ts: parseRepoParam now strips a single leading slash and collapses consecutive slashes via regex before running the existing owner/repo validation regex
• test/repo-analytics-utils-sanitize.test.ts (new): covers leading slash, double slashes, mixed slashes + surrounding spaces, and unchanged normal input

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How to Test

1. Checkout this branch
2. Run npx vitest run test/repo-analytics-utils-sanitize.test.ts test/repo-analytics-utils.test.ts
3. Confirm all 23 tests pass (19 pre-existing + 4 new)

Expected result: parseRepoParam("/owner/repo") and parseRepoParam("owner//repo") both return { owner: "owner", repo: "repo" } instead of null, while all pre-existing valid/invalid cases still behave the same.

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Screenshots / Recordings

Not applicable — no UI impact, logic-only change.

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Checklist

• Linked the related issue above
• Self-reviewed my own diff
• No unnecessary console.log, debug code, or commented-out blocks
• npm run lint passes locally
• No TypeScript errors (npm run type-check)
• Added or updated tests where applicable
• Updated documentation / comments if behavior changed

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Accessibility (UI changes only)

Not applicable — no UI impact.

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Additional Context

None.

[github-actions]

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