fix(cache): invalidate link resolution cache on update and delete

[RaoUsama7]

• Add reusable helper for Redis link-resolution cache invalidation
• Invalidate cached keys after successful link update and delete
• Clear both old and new key sets when template association changes
• Add unit tests for cache invalidation helper behavior

Description

Fix stale redirect and SDK resolve behavior by invalidating Redis link-resolution cache entries when links are updated or deleted.

Previously, the read path cached link JSON for 5 minutes, but link mutation routes did not invalidate those keys. This meant stale redirects or stale SDK resolutions could be served until TTL expiry.

This change adds a small reusable cache invalidation helper and applies it to link update/delete flows.

Type of Change

• Bug fix / correctness improvement
• New feature
• Breaking change
• Documentation update

Changes Made

• Add invalidateLinkResolutionCache helper for Redis link-resolution cache keys
• Invalidate cached link-resolution keys after successful link update
• Invalidate both old and new key sets when template association changes
• Invalidate cached link-resolution keys after successful link delete
• Add unit tests for cache invalidation helper behavior

Notes

• Scope is intentionally minimal and correctness-focused
• Does not change redirect read-path behavior
• Does not include stampede protection, negative caching, or broader cache redesign

Testing

• All tests passing locally

[codecov]

Codecov Report

❌ Patch coverage is 40.74074% with 32 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
src/routes/links.ts	0.00%	32 Missing ⚠️

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