Flatten repo structure: move crawler/ to root, remove vqa/ and immoweb/

The crawler subdirectory was the only active project. Moving it to the
repo root simplifies paths and removes the unnecessary nesting. The
vqa/ and immoweb/ directories were legacy/unused and have been removed.

Updated .drone.yml, .gitignore, .claude/ docs, and skills to reflect
the new flat structure.

tests/unit/test_redis_lock.py

@@ -0,0 +1,74 @@
+"""Unit tests for Redis distributed lock."""
+from unittest import mock
+
+import pytest
+
+from utils.redis_lock import redis_lock, get_redis_client
+
+
+class TestRedisLock:
+    """Tests for redis_lock context manager."""
+
+    @mock.patch("utils.redis_lock.get_redis_client")
+    def test_lock_acquired_successfully(self, mock_get_client):
+        """Test lock acquisition when no other lock exists."""
+        mock_client = mock.MagicMock()
+        mock_client.set.return_value = True
+        mock_get_client.return_value = mock_client
+
+        with redis_lock("test_lock") as acquired:
+            assert acquired is True
+
+        mock_client.set.assert_called_once_with("lock:test_lock", "1", nx=True, ex=3600 * 4)
+        mock_client.delete.assert_called_once_with("lock:test_lock")
+
+    @mock.patch("utils.redis_lock.get_redis_client")
+    def test_lock_not_acquired(self, mock_get_client):
+        """Test lock not acquired when another lock exists."""
+        mock_client = mock.MagicMock()
+        mock_client.set.return_value = None  # Redis returns None when nx=True fails
+        mock_get_client.return_value = mock_client
+
+        with redis_lock("test_lock") as acquired:
+            assert acquired is False
+
+        mock_client.set.assert_called_once_with("lock:test_lock", "1", nx=True, ex=3600 * 4)
+        # Should NOT call delete since we didn't acquire the lock
+        mock_client.delete.assert_not_called()
+
+    @mock.patch("utils.redis_lock.get_redis_client")
+    def test_lock_released_on_exception(self, mock_get_client):
+        """Test lock is released even when exception occurs."""
+        mock_client = mock.MagicMock()
+        mock_client.set.return_value = True
+        mock_get_client.return_value = mock_client
+
+        with pytest.raises(ValueError):
+            with redis_lock("test_lock") as acquired:
+                assert acquired is True
+                raise ValueError("Test error")
+
+        # Lock should still be released
+        mock_client.delete.assert_called_once_with("lock:test_lock")
+
+    @mock.patch("utils.redis_lock.get_redis_client")
+    def test_custom_timeout(self, mock_get_client):
+        """Test lock with custom timeout."""
+        mock_client = mock.MagicMock()
+        mock_client.set.return_value = True
+        mock_get_client.return_value = mock_client
+
+        with redis_lock("test_lock", timeout=300) as acquired:
+            assert acquired is True
+
+        mock_client.set.assert_called_once_with("lock:test_lock", "1", nx=True, ex=300)
+
+    @mock.patch("utils.redis_lock.redis")
+    def test_get_redis_client_uses_broker_url(self, mock_redis):
+        """Test Redis client is created from CELERY_BROKER_URL."""
+        with mock.patch.dict("os.environ", {"CELERY_BROKER_URL": "redis://testhost:1234/5"}):
+            get_redis_client()
+
+        mock_redis.from_url.assert_called_once_with(
+            "redis://testhost:1234/5", decode_responses=True
+        )