Reorganize into monorepo layout, move mitarbeiter-app to legacy reference

Consolidates the previously separate omsorgapp and omsorgCore repos
(each had their own nested .git with GitHub history) plus the old
root-level website/mitarbeiter-app into a single monorepo, matching
the structure already documented in the root CLAUDE.md. Also moves
the PHP employee app aside as omsorgWeb/mitarbeiter-app-legacy/ to
serve as a template for a ground-up rewrite.

Fixes .gitignore in the same pass: the config-secrets/uploads/data
patterns were unanchored (relative to repo root, not depth-agnostic),
so they silently stopped matching once the app moved under omsorgWeb/.
Patterns are now **/-prefixed and cover both mitarbeiter-app and
mitarbeiter-app-legacy, keeping DB/SMTP credentials and uploaded
employee documents out of version control.

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

omsorgWeb/mitarbeiter-app-legacy/manifest.webmanifest

@@ -0,0 +1,12 @@
+{
+  "name": "OMSORG Mitarbeiter-App",
+  "short_name": "OMSORG",
+  "start_url": "./",
+  "display": "standalone",
+  "background_color": "#ffffff",
+  "theme_color": "#1a3a5c",
+  "icons": [
+    { "src": "../assets/omsorg-logo-new.png", "sizes": "192x192", "type": "image/png" },
+    { "src": "../assets/omsorg-logo-new.png", "sizes": "512x512", "type": "image/png" }
+  ]
+}