feat(desktop): fire cron jobs from the dashboard backend

The cron scheduler tick loop only ran inside `hermes gateway run`, but the
desktop app spawns a `hermes dashboard` backend with no gateway — so any cron
a user created in the app was saved and never fired (silently).

Run a minimal scheduler ticker inside the dashboard lifespan, gated on a new
HERMES_DESKTOP=1 marker the electron shell injects, so server `hermes dashboard`
is unaffected. Cross-process safe via the existing cron/.tick.lock, so it never
double-fires alongside a real gateway.

apps/desktop/electron/main.cjs

@@ -4274,6 +4274,9 @@ async function spawnPoolBackend(profile, entry) {
       HERMES_HOME,
       ...backend.env,
       HERMES_DASHBOARD_SESSION_TOKEN: token,
+      // Marks this dashboard backend as desktop-spawned so it runs the cron
+      // scheduler tick loop (the gateway isn't running under the app).
+      HERMES_DESKTOP: '1',
       HERMES_WEB_DIST: webDist
     },
     shell: backend.shell,
@@ -4415,6 +4418,9 @@ async function startHermes() {
         HERMES_HOME,
         ...backend.env,
         HERMES_DASHBOARD_SESSION_TOKEN: token,
+        // Marks this dashboard backend as desktop-spawned so it runs the cron
+        // scheduler tick loop (the gateway isn't running under the app).
+        HERMES_DESKTOP: '1',
         HERMES_WEB_DIST: webDist
       },
       shell: backend.shell,