feat: settle Chrome and notifications into the classroom look

Chrome stays a full browser. The managed policy only removes the things
a volunteer should never be asked about — the first-run tour, the
default-browser prompt, sync and sign-in promos, the profile picker —
and pins the Home button to Wonder Ink so there is always one obvious
way back. Startup URL is a recommended policy rather than a managed one,
so a teacher can still change it. Nothing restricts where they browse,
and the profile is untouched, so YouTube and other logins survive
reboots and updates.

Notifications were still stock mako, which looked nothing like the rest
of the shell. Give them the dock's palette: the same dark slate, the
same hairline white border, rounded, white text, top right. Kept a
little more opaque than the dock so text stays readable over video, and
on the overlay layer so a parent-call alert can still reach someone
watching a fullscreen DVD.

mako was only ever reaching the session through D-Bus activation. Start
it from the sway config so it is running before anything needs it.

classroom-notify-test sends a sample so the styling can be checked
without waiting for a real event.

Co-Authored-By: Claude Opus 5 <[email protected]>

packaging/debian/postinst

@@ -19,6 +19,7 @@ chmod 0644 /home/classroom/.bash_profile
 
 chmod 0755 /usr/local/bin/classroom-browser
 chmod 0755 /usr/local/bin/classroom-window
+chmod 0755 /usr/local/bin/classroom-notify-test
 
 if [ ! -f /etc/ekklesia-classroom/device.conf ]; then
     cat > /etc/ekklesia-classroom/device.conf <<'CONFIG'