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

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

@@ -0,0 +1,39 @@
+package agzam.vyatsu.data.local
+
+import androidx.room.Dao
+import androidx.room.Insert
+import androidx.room.OnConflictStrategy
+import androidx.room.Query
+import kotlinx.coroutines.flow.Flow
+
+@Dao
+interface TeacherDao {
+    @Query("SELECT * FROM departments ORDER BY name")
+    fun observeDepartments(): Flow<List<DepartmentEntity>>
+
+    @Query("SELECT * FROM departments WHERE departmentId = :id")
+    suspend fun getDepartment(id: String): DepartmentEntity?
+
+    @Insert(onConflict = OnConflictStrategy.REPLACE)
+    suspend fun insertAll(departments: List<DepartmentEntity>)
+
+    @Query("SELECT MAX(lastSyncedAt) FROM departments")
+    suspend fun maxSyncedAt(): Long?
+
+    @Query("SELECT DISTINCT faculty FROM departments ORDER BY faculty")
+    suspend fun getFaculties(): List<String>
+
+    @Query("DELETE FROM department_periods")
+    suspend fun deleteAllPeriods()
+
+    @Insert(onConflict = OnConflictStrategy.REPLACE)
+    suspend fun insertPeriods(periods: List<DepartmentPeriodEntity>)
+
+    @Query(
+        "SELECT * FROM department_periods WHERE weekStart <= :epochDay AND weekEnd >= :epochDay ORDER BY departmentId"
+    )
+    suspend fun getPeriodsForDate(epochDay: Long): List<DepartmentPeriodEntity>
+
+    @Query("SELECT * FROM department_periods WHERE departmentId = :departmentId ORDER BY weekStart")
+    suspend fun getPeriodsForDepartment(departmentId: String): List<DepartmentPeriodEntity>
+}