feat: Initial Database stuff for FolderPairs

This commit adds the initial Database design to save and load `FolderPair`s locally

app/src/main/java/com/fabisahne/cloudsync/data/FolderPairDao.kt

@@ -0,0 +1,26 @@
+package com.fabisahne.cloudsync.data
+
+import androidx.room.Dao
+import androidx.room.Delete
+import androidx.room.Insert
+import androidx.room.Query
+import androidx.room.Update
+import kotlinx.coroutines.flow.Flow
+
+@Dao
+interface FolderPairDao {
+    @Query("SELECT * FROM folder_pairs ORDER BY createdAt DESC")
+    fun getAll(): Flow<List<FolderPair>>
+
+    @Query("SELECT * FROM folder_pairs WHERE id = :id")
+    suspend fun getById(id: Long): FolderPair?
+
+    @Insert
+    suspend fun insert(folderPair: FolderPair): Long
+
+    @Update
+    suspend fun update(folderPair: FolderPair)
+
+    @Delete
+    suspend fun delete(folderPair: FolderPair)
+}