Add unit tests and Gitea CI workflow for bug fixes

- Add fetcher/tests/ with 21 tests covering all bug fixes:
  - test_utils: get_with_protocol URL normalization (5 tests)
  - test_config: scheduled_tasks.json PK uniqueness, Celery queue
    settings (7 tests)
  - test_publish: URL routing and view for /task/publish_<id>/ (4 tests)
  - test_template_field: url_detail.html renders images_url field (2 tests)
  - test_search_postprocess: URL host filtering and param stripping (3 tests)
- Replace empty fetcher/tests.py with tests/ package
- Add .gitea/workflows/test.yml: runs on PRs and pushes to main,
  installs dependencies and runs `manage.py test fetcher.tests`

app_urls/fetcher/tests/test_utils.py

@@ -0,0 +1,22 @@
+from django.test import SimpleTestCase
+from ..src.utils import get_with_protocol
+
+
+class GetWithProtocolTests(SimpleTestCase):
+    def test_missing_protocol_prepends_https(self):
+        self.assertEqual(get_with_protocol("example.com"), "https://example.com")
+
+    def test_missing_protocol_with_path(self):
+        self.assertEqual(
+            get_with_protocol("example.com/article"),
+            "https://example.com/article",
+        )
+
+    def test_upgrades_http_to_https(self):
+        self.assertEqual(get_with_protocol("http://example.com"), "https://example.com")
+
+    def test_preserves_https(self):
+        self.assertEqual(get_with_protocol("https://example.com"), "https://example.com")
+
+    def test_empty_string_becomes_https(self):
+        self.assertEqual(get_with_protocol(""), "https://")