chore(deps): bump knip 6.14.1 → 6.14.2 and docker/metadata-action v5 → v6

Both are Dependabot bumps that have been waiting on the queue; landing
them directly so the lock files stay coherent with the rest of v1.5.5.

knip: minor; docker/metadata-action: clean major (workflow change is
exactly the @v5 → @v6 string in two places).

Closes #209
Closes #183

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

package.json

@@ -104,7 +104,7 @@
     "@vitest/coverage-v8": "^4.1.5",
     "eslint": "^9",
     "eslint-config-next": "16.2.6",
-    "knip": "^6.14.1",
+    "knip": "^6.14.2",
     "pdf-parse": "^2.4.5",
     "pg": "^8.20.0",
     "prettier": "^3.8.3",