docs: cut to v0.9.0 with unified .de/.en naming

- Remove all prior release notes and version snapshots (v0.6.0-v0.8.6)
- Rename handbook to *.de.md; keep *.en.md
- New release notes v0.9.0.de.md/.en.md with v0.9.0 snapshot
- generate-docs.mjs: .de/.en convention incl. search index and en-fallback
- docs.tsx: release fallback now uses version.de.md
- Wording: neutral tagline, anonymous user, no gender forms
- Add docs/examples/import-tools.yaml and link from administration docs

docs/handbook/administration.en.md

@@ -73,6 +73,9 @@ Central access to the tool catalog.
     category: Monitoring
   ```
 
+  A larger, ready-to-import example file is located at
+  `docs/examples/import-tools.yaml` (24 common enterprise tools).
+
   During import, individual faulty rows are skipped and listed with their row
   number; correct rows are still created. Every import produces audit-log
   entries.