App 2.35.2: a round full-screen button; THEMES.md with every Overview style

The full-screen button's disc was an oval (an even inset in a 64 x 72 dp
area); the area is now a square 72 dp, pulled into the panel's padding
so the logo keeps its line. THEMES.md shows the twelve Overview styles,
each with and without the navigation (emulator, sample values), with
what inspired each; linked from README.md and AGENTS.md.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01LhzAVaUyqcw5PkGjz4mWW6

app/build.gradle

@@ -34,8 +34,8 @@ android {
         applicationId "com.stinnesbeck.nilsmg4"
         minSdk 27
         targetSdk 36
-        versionCode 136
-        versionName "2.35.1"
+        versionCode 137
+        versionName "2.35.2"
 
         // Nothing about the server ships in the APK: its URL and ingest token are entered in
         // the app's Server tab (ServerConfig), and the database is only reachable by the server.