fix: add Linux camera browser fallback

[kamjin3086]

This PR extracts the Linux camera fallback work from #283, following the request to split it from the Fedora RPM packaging changes.

Summary:

• detect desktop WebViews that do not expose RTCPeerConnection
• show an external browser fallback action for the camera stream
• add a Tauri command that writes and opens a temporary browser-based camera viewer
• keep this PR free of RPM/release workflow changes

Validation:

• cargo check -q
• yarn --ignore-engines typecheck
• yarn --ignore-engines lint (passes with existing repository warnings only)
• git diff --check

Notes:

• While splitting the PR, I added the missing GstWebRTCProducer.meta type so the branch passes TypeScript checking.

[kamjin3086]

Update: I installed the missing Fedora development packages locally and reran the checks. cargo check -q now passes for this branch, so I removed the previous environment-blocked note and updated the PR description with the full validation list.

[FabienDanieau]

Super nice, it's really useful. I've left some comments.

[kamjin3086]

Thanks for the review, I updated the PR to address both points:

• The external browser camera page now embeds and uses the existing src/lib/gstwebrtc-api.js helper instead of manually duplicating the signaling / WebRTC session logic.
• The camera fallback display now also relies on the shared isWebRTCAvailable state, while still limiting the browser fallback button to the desktop WebView unsupported case.

I reran the local checks after the change:

• cargo fmt --check
• cargo check -q
• yarn --ignore-engines typecheck
• yarn --ignore-engines lint (passes with the existing warnings)

Let me know if you would prefer the external viewer glue to be factored further, but this should now avoid the duplicated low-level WebRTC logic.

[FabienDanieau]

Just a minor refacto and we can merge!

[FabienDanieau]

you may compare to this variable https://github.com/kamjin3086/reachy-mini-desktop-app/blob/396941ea78e9cadb53612a61e86b040a4d555328/src/contexts/WebRTCStreamContext.tsx#L38 instead of the string

[kamjin3086]

Thanks, fixed in the latest commit.

I exported the existing WEBRTC_UNSUPPORTED_MESSAGE constant from WebRTCStreamContext and now compare against that in CameraFeed instead of duplicating the literal string.

I reran the checks locally:

• yarn --ignore-engines typecheck
• yarn --ignore-engines lint (passes with the existing warnings)
• cargo fmt --check
• cargo check -q

Thanks again for the review!

[FabienDanieau]

Thanks! Let's merge