Fix #7: increase FPS spinbox maximum to 999

The maxFPSSpinBox had no explicit maximum, defaulting to Qt's 99.
Users with high-refresh displays could set FPS > 99 in config.inp
but couldn't change it in the UI without editing the file.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: 2 people

src/common/qprojectmconfigdialog.ui

@@ -296,6 +296,9 @@ p, li { white-space: pre-wrap; }
       <property name="minimum">
        <number>0</number>
       </property>
+      <property name="maximum">
+       <number>999</number>
+      </property>
      </widget>
     </item>
     <item row="6" column="0" colspan="2">