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>

app/cypress/e2e/navbar_logo_visibility.spec.js

@@ -15,7 +15,7 @@ describe('Navbar Logo Visibility', () => {
 
   it('should become visible (opacity 1) after entering fullscreen', () => {
     cy.window().then(win => {
-      win.fullscreen();
+      win.enterFullscreen();
     });
     cy.get('#navbar_logo', { timeout: 4000 })
       .should('have.css', 'opacity', '1');
@@ -23,7 +23,7 @@ describe('Navbar Logo Visibility', () => {
 
   it('should become invisible again (opacity 0) after exiting fullscreen', () => {
     cy.window().then(win => {
-      win.fullscreen();
+      win.enterFullscreen();
       win.exitFullscreen();
     });
     cy.get('#navbar_logo', { timeout: 4000 })