feat: migrate to pyproject.toml, add test suites, split CI workflows

- Replace requirements.txt with pyproject.toml for modern Python packaging
- Add unit, integration, lint and security test suites under tests/
- Add utils/export_runtime_requirements.py and utils/check_hadolint_sarif.py
- Split monolithic CI into reusable lint.yml, security.yml and tests.yml
- Refactor ci.yml to orchestrate reusable workflows; publish on semver tag only
- Modernize Dockerfile: pin python:3.12-slim, install via pyproject.toml
- Expand Makefile with lint, security, test and CI targets
- Add test-e2e via act with portfolio container stop/start around run
- Fix navbar_logo_visibility.spec.js: win.fullscreen() → win.enterFullscreen()
- Set use_reloader=False in app.run() to prevent double-start in CI
- Add app/core.* and build artifacts to .gitignore
- Fix apt-get → sudo apt-get in tests.yml e2e job
- Fix pip install --ignore-installed to handle stale act cache

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

tests/lint/test_test_file_naming.py

@@ -0,0 +1,25 @@
+import unittest
+from pathlib import Path
+
+
+class TestTestFileNaming(unittest.TestCase):
+    def test_all_python_files_use_test_prefix(self):
+        tests_root = Path(__file__).resolve().parents[1]
+        invalid_files = []
+
+        for path in tests_root.rglob("*.py"):
+            if path.name == "__init__.py":
+                continue
+
+            if not path.name.startswith("test_"):
+                invalid_files.append(path.relative_to(tests_root).as_posix())
+
+        self.assertFalse(
+            invalid_files,
+            "The following Python files do not start with 'test_':\n"
+            + "\n".join(f"- {path}" for path in invalid_files),
+        )
+
+
+if __name__ == "__main__":
+    unittest.main()