feat(tailscale): add Tailscale control center widget

[Gdetrane]

Summary

Native Tailscale integration as a builtin control center plugin — search, filter,
and copy IPs or FQDNs of any node in the tailnet without opening the web admin
panel or using the CLI.

Motivation

Tailscale is a rapidly growing mesh VPN with a vibrant community, now shipping by
default in distros like Bazzite and other Fedora variants. Existing desktop
integrations (e.g., GNOME extensions) are limited and unreliable. This widget
provides quick, native access to tailnet device information directly from the DMS
control center.

Changes

Go backend (core/internal/server/tailscale/)

• Local API client — polls /var/run/tailscale/tailscaled.sock via HTTP over
  Unix socket, no CLI shelling or external dependencies
• Status parsing — converts /localapi/v0/status into lean state structs with
  peer sorting (online first, alphabetical), user ID resolution, mobile hostname
  fixup (localhost to DNS-derived name), and relative time formatting
• IPC methods — tailscale.subscribe (streaming state updates),
  tailscale.getStatus (one-shot), tailscale.refresh (manual poll)
• Daemon lifecycle handling — eager init with 30s background retry when
  tailscaled is not running at startup; polls keep running through daemon
  stop/restart cycles for automatic recovery
• 18 unit tests covering status parsing, peer sorting, manager lifecycle,
  handler routing, and edge cases

QML frontend

• TailscaleService singleton with ref counting and subscription management
  following the CupsService pattern
• TailscaleWidget PluginComponent with control center tile (device_hub icon,
  online peer count) and expandable detail view
• Filter chips — My Online / Online / All with live device counts using
  DankFilterChips
• Searchable device list — fuzzy match on hostname, DNS name, and IP
• Copy-to-clipboard buttons for Tailscale IPs and DNS names
• Self device highlighted with accent tint and This device badge
• Expandable cards showing DNS name, tags, owner, relay/direct info
• All strings use I18n.tr() with translator context per CONTRIBUTING.md

Integration

• Widget registered in WidgetModel.qml with DragDropGrid and DetailHost wiring
• DMSService.qml signal added for tailscale state updates
• DetailHost.qml height set to 350px (matching Bluetooth/VPN)

Daemon lifecycle handling

• Tailscale running at startup: widget shows immediately
• Tailscale started after DMS: widget appears within 30s (retry loop)
• Tailscale stopped while running: widget shows Disconnected within 30s
• Tailscale restarted: widget recovers automatically within 30s
• Tailscale not installed: widget shows Not available, no errors

Test plan

• Unit tests pass (make test, pre-commit hooks pass)
• Widget appears when Tailscale is running
• Widget shows Not available when Tailscale is not installed
• Filter chips filter correctly (My Online / Online / All)
• Search filters by hostname, IP, and DNS name
• Copy buttons copy correct values to clipboard
• Self device shows with accent highlight and This device badge
• Expanding a card reveals DNS name, tags, owner
• Daemon stop: widget shows Disconnected
• Daemon restart: widget recovers automatically
• DMS started without Tailscale, Tailscale started later: widget appears
• Mobile devices show proper names (not localhost)

Tested on:

• Desktop (RTX 2070S), CachyOS (Arch), DMS (git) v1.4.0, niri
• ThinkPad X390, CachyOS (Arch), DMS (git) v1.4.0, niri

[Purian23]

Hi there, thanks for the PR. I think this is better suited as an optional plug-in rather a native DMS feature as it's best fit for a select number of users. I will refer to @bbedward for a final accessment.

[Gdetrane]

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Let me know if you want to see more screenshots

[Gdetrane]

@Purian23 Hi, thanks for jumping in, that's fair. I thought this could be a nice built-in feature, given Tailscale's growth and it being included in some distros, but I totally see your point.

I'm still new to this repo, but I imagine this would require keeping the core Go logic and moving the QML logic to a plugin package, right?

Any feedback is welcome

[mecattaf]

I would 100% use that!

[Gdetrane]

Thanks @mecattaf I really appreciate that 😄
I moved everything to Tailscale, it's brilliant and genuinely love it. It's exploding in popularity, I work at Red Hat and I know that in the Fedora world it's starting to get a lot of traction, see https://universal-blue.org/
If I'm not mistaken it's pre-installed in all their variants. One day I'd be very happy to see an official DMS flavor of Fedora btw 😎

[mecattaf]

Thanks @mecattaf I really appreciate that 😄
I moved everything to Tailscale, it's brilliant and genuinely love it. It's exploding in popularity, I work at Red Hat and I know that in the Fedora world it's starting to get a lot of traction, see https://universal-blue.org/

Been a ublue user for 5+ years! Specifically have my own bluebuild recipe

If I'm not mistaken it's pre-installed in all their variants. One day I'd be very happy to see an official DMS flavor of Fedora btw 😎

Actually DMS ships with the miracle window manager official distro but that's super niche. Otherwise check out Zirconium (dms + niri)