refactor: migrate preferences to DataStore and decouple core:domain for KMP (#4731)

core/common/src/commonMain/kotlin/org/meshtastic/core/common/database/DatabaseManager.kt

@@ -0,0 +1,34 @@
+/*
+ * Copyright (c) 2025-2026 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.database
+
+import kotlinx.coroutines.flow.StateFlow
+
+/** Interface for managing database instances and cache limits. */
+interface DatabaseManager {
+    /** Reactive stream of the current database cache limit. */
+    val cacheLimit: StateFlow<Int>
+
+    /** Returns the current database cache limit from storage. */
+    fun getCurrentCacheLimit(): Int
+
+    /** Sets the database cache limit. */
+    fun setCacheLimit(limit: Int)
+
+    /** Switches the active database to the one associated with the given [address]. */
+    suspend fun switchActiveDatabase(address: String?)
+}