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>

Dockerfile

@@ -1,14 +1,16 @@
-# Base image for Python
-FROM python:slim
+FROM python:3.12-slim
+
+ENV PYTHONDONTWRITEBYTECODE=1 \
+    PYTHONUNBUFFERED=1 \
+    FLASK_HOST=0.0.0.0
+
+WORKDIR /tmp/build
+
+COPY pyproject.toml README.md main.py ./
+COPY app ./app
+RUN python -m pip install --no-cache-dir .
 
-# Set the working directory
 WORKDIR /app
-
-# Copy and install dependencies
-COPY app/requirements.txt requirements.txt
-RUN pip install --no-cache-dir -r requirements.txt
-
-# Copy application code
 COPY app/ .
 
 CMD ["python", "app.py"]