v0.3.0

Minor release since v0.2.0:

- Configurable site logo and favicon (AXGIT_LOGO/AXGIT_LOGO_LINK/AXGIT_FAVICON),
  served via GET /api/v1/site/logo and GET /api/v1/site/favicon and rendered
  in the web header (docs/DECISIONS.md #81/#82).
- Repository page titles now compose from the configured site title instead
  of a baked-in "— Axgit" suffix.