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/migrations/004_login_attempts.php

@@ -0,0 +1,13 @@
+<?php
+return [
+    'description' => 'Login attempts table for IP-based rate limiting',
+    'up' => [
+        "CREATE TABLE IF NOT EXISTS login_attempts (
+            id           INT          NOT NULL AUTO_INCREMENT PRIMARY KEY,
+            ip           VARCHAR(45)  NOT NULL DEFAULT '',
+            username     VARCHAR(190) NOT NULL DEFAULT '',
+            attempted_at VARCHAR(32)  NOT NULL DEFAULT ''
+        )",
+        "CREATE INDEX idx_login_attempts_ip_time ON login_attempts (ip, attempted_at)",
+    ],
+];