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

templates/partials/sections/projects.html

@@ -32,6 +32,7 @@
             </strong>
             {{if .Current}}<span class="live-badge"><iconify-icon icon="mdi:wifi" width="14" height="14"></iconify-icon>LIVE</span>{{end}}
             {{if .GitRepoUrl}}<a href="{{.GitRepoUrl}}" target="_blank" rel="noopener noreferrer" class="github-badge"><iconify-icon icon="mdi:github" width="14" height="14"></iconify-icon>GitHub</a>{{end}}
+            {{if and .OpenSource .GitRepoUrl}}<a href="{{.GitRepoUrl}}/stargazers" target="_blank" rel="noopener noreferrer" class="stars-badge"><img src="https://img.shields.io/github/stars/{{githubRepo .GitRepoUrl}}?style=flat&logo=github&label=stars" alt="GitHub stars" loading="lazy"></a>{{end}}
             {{if .MaintainedBy}}<span class="maintained-badge">{{$.UI.Sections.MaintainedBy}} {{.MaintainedBy}}</span>{{end}}
             <br>
             <small>{{if .StartDate}}{{.StartDate}}{{if .Current}}{{if .DynamicDate}} / {{.DynamicDate}}{{else}} / {{$.UI.Sections.Present}}{{end}}{{end}}{{end}} - ({{.Location}})</small>