feat: add buildCacheKey helper for deterministic cache keys (#577)

[Killerjunior]

Summary

Closes #577

• Implemented buildCacheKey(base: string, params: Record<string, unknown>): string helper in cache-key-params.utils.ts to generate deterministic, fixed-length cache keys from a base string and query param set.
• Ensured param keys are sorted lexicographically prior to SHA-256 hashing so query parameter order does not affect the output cache key.
• Added comprehensive unit tests in cache-key-params.utils.test.ts verifying identical keys for reordered params, different keys for distinct params, and fixed-length formatting.

Testing

• pnpm lint
• pnpm build
• pnpm exec prisma generate when schema or generated types changed

Checklist

• Linked issue or backlog item (Add helper for generating a stable cache key from a creator ID and query param set #577)
• No secrets or live credentials added
• Docs updated if setup or env changed
• Change is scoped to one problem