Snap windows to the desktop grid and to whole lines, font size picker (10 to 18), white text in settings dialogs, bump to 0.1.12

- After a move, windows snap to the Windows desktop icon grid; after a resize,
  the window height is trimmed so the scrollback ends on a whole line.
- The font size slider is replaced by square 10 to 18 buttons. Sizes saved by
  the old slider round to the nearest picker size.
- Settings and font dialogs always use white text, so a dark window text color
  no longer makes their labels invisible.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/main/kotlin/ui/MainScreen.kt

@@ -205,9 +205,9 @@ fun MainScreen(
             MaterialTheme(colorScheme = colorScheme) {
                 Surface {
                     Column(modifier = Modifier.fillMaxSize().padding(8.dp).verticalScroll(rememberScrollState())) {
-                        Text("Server messages font:", color = textColor, style = MaterialTheme.typography.bodySmall)
+                        Text("Server messages font:", color = Color.White, style = MaterialTheme.typography.bodySmall)
                         Spacer(Modifier.height(4.dp))
-                        FontPickerList(displaySettings.fontId, textColor, onFontChange)
+                        FontPickerList(displaySettings.fontId, Color.White, onFontChange)
                     }
                 }
             }