D-Bus Phase 3/4: upgrade sessiond, services, add StatusNotifierWatcher, consolidate configs

- redbear-sessiond: add Manager.Inhibit (pipe FD), CanPowerOff/CanReboot/
  CanSuspend/CanHibernate/CanHybridSleep/CanSleep (return na), PowerOff/
  Reboot/Suspend stubs, GetSessionByPID, ListUsers, ListSeats,
  ListInhibitors, ActivateSession/LockSession/UnlockSession/TerminateSession
- redbear-sessiond: add Session SetIdleHint, SetLockedHint, SetType,
  Terminate methods; wire PauseDevice/ResumeDevice/Lock/Unlock signal
  emission via SignalEmitter injection; add dynamic device enumeration
  scanning /scheme/drm/card* and /dev/input/event* at startup
- redbear-sessiond: replace infinite pending() with stoppable shutdown
  via tokio watch channel + control socket shutdown command
- redbear-upower: add Changed signal emission with 30s periodic polling
  and power state snapshot comparison
- redbear-notifications: add ActionInvoked signal, expand capabilities
  to body + body-markup + actions
- redbear-polkit, redbear-udisks: replace pending() with stoppable
  shutdown via signal handling + watch channel
- Add redbear-statusnotifierwatcher: new session bus service implementing
  org.freedesktop.StatusNotifierWatcher for KDE system tray
- Add D-Bus activation file for StatusNotifierWatcher
- KWin session.cpp: try LogindSession before NoopSession fallback
- Consolidate config profiles: remove obsolete redbear-desktop, redbear-kde,
  redbear-live-*, redbear-minimal-*, redbear-wayland configs; simplify
  to three supported targets (redbear-full, redbear-mini, redbear-grub)
- Update DBUS-INTEGRATION-PLAN.md and DESKTOP-STACK-CURRENT-STATUS.md
  with Phase 3/4 fragility assessment, KWin readiness matrix, and
  completeness gap analysis

local/docs/GREETER-LOGIN-IMPLEMENTATION-PLAN.md

@@ -75,9 +75,9 @@ recovery model.
 
 This plan assumes the Red Bear desktop direction converges on **one KDE-on-Wayland path**.
 
-Current implementation answer: the first tracked owner is `redbear-full` (and therefore
-`redbear-live-full` for live media). Older names such as `redbear-kde` may still appear in
-historical or staging material, but they are not the supported compile-target surface for this plan.
+Current implementation answer: the first tracked owner is `redbear-full`. Older names such
+as `redbear-kde` may still appear in historical or staging material, but they are not the
+supported compile-target surface for this plan.
 
 ---
 
@@ -866,8 +866,7 @@ The greeter **recipe**, not the config fragment, should own staged runtime artif
 4. Is `dbus-run-session` reliable enough on Red Bear, or should the current `dbus-launch` path remain the first shipped session-bus strategy?
 5. At what point should the project consider SDDM-class integration again, if ever?
 
-Current answer to (1): **`redbear-full` first**, with `redbear-live-full` inheriting that path for
-live media.
+Current answer to (1): **`redbear-full` first**.
 
 Current answer to (2): **traditional `/etc/shadow` SHA-512-crypt / SHA-256-crypt first** (`$6$` / `$5$`),
 with narrower support preferred over premature multi-format sprawl.