feat: app icon (SVG crow), static file serving, favicon

- Add corvid.svg — stylised blue crow on dark background
- Mount /static via StaticFiles in main.py
- Wire favicon in base.html
- Add aiofiles dep (required by StaticFiles)

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

pyproject.toml

@@ -15,6 +15,7 @@ dependencies = [
     "alembic>=1.14",
     "pydantic>=2.0",
     "jinja2>=3.1",
+    "aiofiles>=24.1",
 ]
 
 [project.optional-dependencies]