Flatpak: self-host VocaHQ remote (Homebrew-tap analogue)

[jatinkrmalik]

Why

Flathub is not a channel (flathub/flathub#9368). Packaging exists under packaging/flatpak/. Release .flatpak bundles (AppImage-style, no auto-update) are tracked in #784.

When we want one-command install + flatpak update, self-host a signed OSTree remote like Mac brew tap vocahq/vocamac:

flatpak remote-add --if-not-exists vocahq https://…/vocahq.flatpakrepo
flatpak install vocahq com.vocalinux.Vocalinux

Users still need the Flathub remote for org.gnome.Platform only.

Done when

• Signed repo published (Pages/CDN/VPS or OCI+Pages)
• .flatpakrepo documented on README / site when ready
• CI publishes on v* (or agreed cadence)
• Flatpak: attach CI .flatpak bundles to GitHub Releases #784 release bundles can remain as a fallback or be deprecated later

Out of scope

• Flathub re-submission
• flat-manager unless static hosting proves painful

Refs

• Parent closed: 📦 Create Flatpak package for universal Linux distribution support #167
• Bridge: Flatpak: attach CI .flatpak bundles to GitHub Releases #784
• Sibling Snap stable: Snap: auto-promote release builds to stable after candidate QA #783