security: untrack DataProtection keys and runtime exports; remove dead legacy controllers

- git rm --cached on committed DataProtection key XMLs (keys/, JobTrackerApi/keys/)
  and daily export JSON snapshots; extend .gitignore so runtime data
  (keys, exports, CV artifacts/exports/benchmarks) can never be committed again.
- Delete root Controller/ stubs: an early prototype compiled by no project
  (JobTrackerApi excludes them; JobTrackerBackend globs only JobTrackerApi/Controllers).
- NOTE: the removed key XMLs remain in git history; rotating DataProtection
  keys on the server is recommended.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

.gitignore

@@ -46,6 +46,13 @@ todo jobtracker.txt
 tmp/
 /tmp/
 
+# Runtime data that must never be committed (DataProtection keys, exports, CV artifacts)
+keys/
+JobTrackerApi/exports/
+JobTrackerApi/CvArtifacts/
+JobTrackerApi/CvExports/
+JobTrackerApi/CvBenchmarks/
+
 # Local app data
 *.db
 *.db-*