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/utils/cache_manager.py

@@ -1,7 +1,9 @@
-import os
 import hashlib
-import requests
 import mimetypes
+import os
+
+import requests
+
 
 class CacheManager:
     def __init__(self, cache_dir="static/cache"):
@@ -9,8 +11,7 @@ class CacheManager:
         self._ensure_cache_dir_exists()
 
     def _ensure_cache_dir_exists(self):
-        if not os.path.exists(self.cache_dir):
-            os.makedirs(self.cache_dir)
+        os.makedirs(self.cache_dir, exist_ok=True)
 
     def clear_cache(self):
         if os.path.exists(self.cache_dir):
@@ -20,8 +21,10 @@ class CacheManager:
                     os.remove(path)
 
     def cache_file(self, file_url):
-        # generate a short hash for filename
-        hash_suffix = hashlib.blake2s(file_url.encode('utf-8'), digest_size=8).hexdigest()
+        hash_suffix = hashlib.blake2s(
+            file_url.encode("utf-8"),
+            digest_size=8,
+        ).hexdigest()
         parts = file_url.rstrip("/").split("/")
         base = parts[-2] if parts[-1] == "download" else parts[-1]
 
@@ -31,7 +34,7 @@ class CacheManager:
         except requests.RequestException:
             return None
 
-        content_type = resp.headers.get('Content-Type', '')
+        content_type = resp.headers.get("Content-Type", "")
         ext = mimetypes.guess_extension(content_type.split(";")[0].strip()) or ".png"
         filename = f"{base}_{hash_suffix}{ext}"
         full_path = os.path.join(self.cache_dir, filename)
@@ -41,5 +44,4 @@ class CacheManager:
                 for chunk in resp.iter_content(1024):
                     f.write(chunk)
 
-        # return path relative to /static/
         return f"cache/{filename}"