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/recipes/system/redbear-sessiond/source/src/runtime_state.rs

@@ -1,5 +1,15 @@
 use std::sync::{Arc, RwLock};
 
+#[derive(Clone, Debug)]
+pub struct InhibitorEntry {
+    pub what: String,
+    pub who: String,
+    pub why: String,
+    pub mode: String,
+    pub pid: u32,
+    pub uid: u32,
+}
+
 #[derive(Clone, Debug)]
 pub struct SessionRuntime {
     pub session_id: String,
@@ -11,6 +21,10 @@ pub struct SessionRuntime {
     pub state: String,
     pub active: bool,
     pub preparing_for_shutdown: bool,
+    pub idle_hint: bool,
+    pub locked_hint: bool,
+    pub session_type: String,
+    pub inhibitors: Vec<InhibitorEntry>,
 }
 
 impl Default for SessionRuntime {
@@ -25,6 +39,10 @@ impl Default for SessionRuntime {
             state: String::from("online"),
             active: true,
             preparing_for_shutdown: false,
+            idle_hint: false,
+            locked_hint: false,
+            session_type: String::from("wayland"),
+            inhibitors: Vec::new(),
         }
     }
 }