fix(#75): replace non-null assertion on simpleName with safe mapNotNull

* ci: prevent concurrency cancellation on rapid main merges

The concurrency group used github.ref which is static for main
(refs/heads/main). When multiple PRs merged rapidly (~2 min apart),
each merge commit cancelled the previous CI run before it could finish.

Fix: use github.sha for push events to main (unique per commit) while
keeping the ref-based group for PR branches (cancels on new commits to
the same PR branch).

* refactor(#82): remove dead SkeletonList/SkeletonCard composables

* fix(#72): echo server's WebSocket close code instead of hardcoded 1000

* fix(#75): replace non-null assertion on simpleName with safe mapNotNull

---------

Co-authored-by: ronia <ronia@m57>
Co-authored-by: M57 <hy4ri@users.noreply.github.com>

app/src/main/java/com/m57/hermescontrol/Navigation.kt

@@ -121,7 +121,7 @@ private val ALL_NAV_ITEMS: List<BottomNavItem> =
 
 /** Lookup: data-object simple name → NavKey (used by bottom-nav config). */
 private val NAV_KEY_BY_NAME: Map<String, NavKey> =
-    ALL_NAV_ITEMS.associate { it.key::class.simpleName!! to it.key }
+    ALL_NAV_ITEMS.mapNotNull { it.key::class.simpleName?.let { name -> name to it.key } }.toMap()
 
 /** Resolve a persisted list of nav-item names to BottomNavItem instances. */
 private fun resolveBottomNavItems(names: List<String>): List<BottomNavItem> =