Config file, user service, and a build container that can see bluez

`--config` reads the same directives as the command line, one per line with
the rest of the line as the command, so a unit can carry the kiosk's events
without shell quoting. presence.service is a systemd --user unit that runs it
from ~/.config/presence/config, restarts on failure, and only starts when the
file exists; config.example is the starting point.

The x86_64 release job failed on makepkg's runtime dependency check because
bluez was not in the container. It is now.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

.gitea/workflows/release.yml

@@ -18,12 +18,13 @@ env:
 
 jobs:
   # runner-1 (Docker on ergo): Arch container on the ubuntu-latest label.
+      # bluez is a runtime depend, but makepkg checks those too
   x86_64:
     runs-on: ubuntu-latest
     container: archlinux:latest
     steps:
       - name: Prepare container
-        run: pacman -Syu --noconfirm --needed base-devel git rust dbus
+        run: pacman -Syu --noconfirm --needed base-devel git rust dbus bluez
       - name: Checkout
         uses: builtin:checkout
       - name: Check tag, PKGBUILD and Cargo.toml agree