feat(db): add teacher schedule tables and Room v4 migration

app/src/main/java/agzam/vyatsu/data/local/PreferencesDao.kt

@@ -28,6 +28,36 @@ interface PreferencesDao {
     @Query("INSERT OR REPLACE INTO preferences(key, value) VALUES('selectedDayDate', :date)")
     suspend fun setSelectedDayDate(date: String)
 
+    @Query("SELECT value FROM preferences WHERE key = 'selectedTeacherId'")
+    suspend fun selectedTeacherId(): String?
+
+    @Query(
+        "INSERT OR REPLACE INTO preferences(key, value) VALUES('selectedTeacherId', :teacherId)"
+    )
+    suspend fun setSelectedTeacherId(teacherId: String)
+
+    @Query("SELECT value FROM preferences WHERE key = 'selectedTeacherWeekStart'")
+    suspend fun selectedTeacherWeekStart(): String?
+
+    @Query(
+        "INSERT OR REPLACE INTO preferences(key, value) VALUES('selectedTeacherWeekStart', :weekStart)"
+    )
+    suspend fun setSelectedTeacherWeekStart(weekStart: String)
+
+    @Query("SELECT value FROM preferences WHERE key = 'selectedTeacherDayDate'")
+    suspend fun selectedTeacherDayDate(): String?
+
+    @Query(
+        "INSERT OR REPLACE INTO preferences(key, value) VALUES('selectedTeacherDayDate', :date)"
+    )
+    suspend fun setSelectedTeacherDayDate(date: String)
+
+    @Query(
+        "DELETE FROM preferences WHERE key IN " +
+            "('selectedTeacherId', 'selectedTeacherWeekStart', 'selectedTeacherDayDate')"
+    )
+    suspend fun clearSelectedTeacher()
+
     @Query("SELECT value FROM preferences WHERE key = 'autoUpdateEnabled'")
     suspend fun autoUpdateEnabled(): String?