Timers: admin "Timer font" option with a monospace choice

A new Display-group select (Default / Monospace) sets the font for the
timer and LTC digits. Monospace keeps the numbers from shifting sideways
as they change — easier to read on a fast-moving countdown or timecode.
Flows through server state → client applies a `tm-mono` class and re-fits
the digit sizing; both timer and LTC values (.tm-time) honor it.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

modules/propresenter-timers/module.json

@@ -42,6 +42,16 @@
       "group": "LTC Timecode",
       "showWhen": "ltcEnabled",
       "default": 1
+    },
+    "timerFont": {
+      "type": "select",
+      "label": "Timer font",
+      "group": "Display",
+      "default": "default",
+      "options": [
+        { "value": "default", "label": "Default (system)" },
+        { "value": "monospace", "label": "Monospace — steadier changing digits" }
+      ]
     }
   }
 }