feat: GitHub stars badge on open-source projects via shields.io

- New openSource field in project model distinguishes OS from private
- shields.io badge shows live star count for open-source projects
- SoundInbox marked as NOT open source (no badge, no stars)
- Immich Photo Manager, Cmux Resurrect, Gotify Commander, CDC Starter Kit → open source
- Stars badge hidden in print view

static/css/03-components/_cv-section.css

@@ -194,6 +194,19 @@
     font-size: 1.2em;
 }
 
+.stars-badge {
+    display: inline-flex;
+    align-items: center;
+    margin-left: 0.3em;
+    vertical-align: middle;
+    text-decoration: none;
+}
+
+.stars-badge img {
+    height: 18px;
+    vertical-align: middle;
+}
+
 .maintained-badge {
     display: inline-block;
     background: #3498db;