feat(ui): add the ToBePlayed logo and name

The logo is a traced SVG whose colors follow the accent color;
violet shows it as designed. Favicon, PWA and Apple icons use
it with fixed colors. The header and landing page say
ToBePlayed instead of Game Log. Below 380 px the header shows
only the logo, and the home link keeps its name for screen
readers.

README.md

@@ -1,7 +1,7 @@
 # To Be Played – Frontend
 
 Web app of **To Be Played**, a Steam backlog tracker: import your Steam library, decide what to play, and track what
-you finished. The app is shown as "Game Log" in the UI, in German and English, light and dark.
+you finished. The UI is in German and English, with light and dark mode.
 
 ![Library](docs/screenshots/library-desktop-dark.png)