refactor: use injected ioDispatcher and ApplicationCoroutineScope (#5167)

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

core/common/src/commonMain/kotlin/org/meshtastic/core/common/di/ApplicationCoroutineScope.kt

@@ -0,0 +1,39 @@
+/*
+ * Copyright (c) 2026 Meshtastic LLC
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+package org.meshtastic.core.common.di
+
+import kotlinx.coroutines.CoroutineScope
+import kotlinx.coroutines.SupervisorJob
+import org.koin.core.annotation.Single
+import org.meshtastic.core.common.util.ioDispatcher
+
+/**
+ * A process-wide [CoroutineScope] that outlives individual ViewModels and UI components.
+ *
+ * Use this scope for fire-and-forget cleanup work that must continue after a ViewModel's own scope has been cancelled
+ * (for example, deleting temporary files in `onCleared()`). Backed by a [SupervisorJob] so failures in one child do not
+ * cancel siblings, and by [ioDispatcher] so work runs off the main thread.
+ *
+ * Prefer scoping work to a more specific scope (like `viewModelScope`) whenever possible; this scope is an escape hatch
+ * and should be used sparingly.
+ */
+interface ApplicationCoroutineScope : CoroutineScope
+
+@Single(binds = [ApplicationCoroutineScope::class])
+internal class ApplicationCoroutineScopeImpl : ApplicationCoroutineScope {
+    override val coroutineContext = SupervisorJob() + ioDispatcher
+}