art: add missing icons for TagProjects, Rollback, SetStatus (#60)

Create silo-tag.svg, silo-rollback.svg, and silo-status.svg in the
Catppuccin Mocha style matching existing silo icons. These were
referenced by _icon() but did not exist, causing the commands to
render without toolbar icons.

freecad/resources/icons/silo-rollback.svg

@@ -0,0 +1,8 @@
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 24 24" fill="none" stroke="#cba6f7" stroke-width="2" stroke-linecap="round" stroke-linejoin="round">
+  <!-- Counter-clockwise arrow -->
+  <polyline points="1 4 1 10 7 10" stroke="#f38ba8"/>
+  <path d="M3.51 15a9 9 0 1 0 2.13-9.36L1 10" stroke="#cba6f7"/>
+  <!-- Clock hands -->
+  <line x1="12" y1="7" x2="12" y2="12" stroke="#89dceb" stroke-width="1.5"/>
+  <line x1="12" y1="12" x2="15" y2="14" stroke="#89dceb" stroke-width="1.5"/>
+</svg>

freecad/resources/icons/silo-status.svg

@@ -0,0 +1,7 @@
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 24 24" fill="none" stroke="#cba6f7" stroke-width="2" stroke-linecap="round" stroke-linejoin="round">
+  <!-- Shield shape -->
+  <path d="M12 22s8-4 8-10V5l-8-3-8 3v7c0 6 8 10 8 10z" fill="#313244"/>
+  <!-- Status bars -->
+  <line x1="8" y1="10" x2="16" y2="10" stroke="#a6e3a1" stroke-width="1.5"/>
+  <line x1="8" y1="14" x2="13" y2="14" stroke="#89dceb" stroke-width="1.5"/>
+</svg>

freecad/resources/icons/silo-tag.svg

@@ -0,0 +1,6 @@
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 24 24" fill="none" stroke="#cba6f7" stroke-width="2" stroke-linecap="round" stroke-linejoin="round">
+  <!-- Tag shape -->
+  <path d="M20.59 13.41l-7.17 7.17a2 2 0 0 1-2.83 0L2 12V2h10l8.59 8.59a2 2 0 0 1 0 2.82z" fill="#313244"/>
+  <!-- Tag hole -->
+  <circle cx="7" cy="7" r="1.5" fill="#cba6f7" stroke="none"/>
+</svg>