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>

.gitignore

@@ -1,13 +1,13 @@
 # Config with credentials
-mitarbeiter-app/config.php
-mitarbeiter-app/config.secret.php
+**/mitarbeiter-app*/lib/config.php
+**/mitarbeiter-app*/lib/config.secret.php
 
 # Uploaded files
-mitarbeiter-app/uploads/
-mitarbeiter-app/downloads/
-mitarbeiter-app/fortbildung-materials/
-mitarbeiter-app/assets/avatars/
-mitarbeiter-app/data/
+**/mitarbeiter-app*/uploads/
+**/mitarbeiter-app*/downloads/
+**/mitarbeiter-app*/fortbildung-materials/
+**/mitarbeiter-app*/assets/avatars/
+**/mitarbeiter-app*/data/
 
 # OS / editor
 .DS_Store
@@ -19,3 +19,7 @@ Thumbs.db
 
 # Logs
 *.log
+
+# .NET (omsorgCore)
+omsorgCore/**/bin/
+omsorgCore/**/obj/