chore(java): consolidate mss-failsafe to single canonical copy

Replace the stale multi-module java/mss-failsafe skeleton (old user-management
prototype) with the active single-module machine-safety inspection app that was
living in its own standalone repo at the repo root.

- Remove old java/mss-failsafe/ multi-module tree (mss, userdata, userManagement,
  mssfailsafe.datalayer, mssfailsafeWeblayer) incl. committed build artifacts
- Add the active app (PrimeFaces 11 / JSF 2.3 / Hibernate 5.6 / iText / POI)
  flattened into java/mss-failsafe/ as the only mss-failsafe in git
- Working tree captured = master tip 2a142b5 + in-progress uncommitted work
  (incl. .github/*.instructions.md AI-context files)
- Archive the standalone repo's 33-commit history in GIT_HISTORY_ARCHIVE.md
  since its .git was not migrated

This is the source of truth / base for the upcoming upgraded rewrite.

java/mss-failsafe/.gitignore

@@ -0,0 +1,21 @@
+# Maven Build-Verzeichnis
+target/
+/target/
+
+# IDE-spezifische Dateien
+.idea/
+.vscode/
+*.iml
+*.ipr
+*.iws
+
+# OS-spezifische Dateien
+.DS_Store
+Thumbs.db
+
+# Logs
+*.log
+
+# Temporäre Dateien
+*.tmp
+*.temp