Data layer: Room entities, DAOs, database with exported schema

Milestone 2. Medication / DoseTime / DoseLog per the brief's model.
DoseLog.doseTimeId is SET_NULL (schedule edits must not erase adherence
history) while medId CASCADEs; DoseLog.amount is snapshotted at logging
time so later dose changes don't rewrite the record. Inventory decrement
is a single SQL UPDATE clamped at 0 to stay race-free under escalating
notifications. Enums stored as TEXT; schema exported to app/schemas as
the migration baseline.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

app/src/main/java/no/naiv/meddetsamme/data/MedDatabase.kt

@@ -0,0 +1,38 @@
+package no.naiv.meddetsamme.data
+
+import android.content.Context
+import androidx.room.Database
+import androidx.room.Room
+import androidx.room.RoomDatabase
+
+/**
+ * exportSchema=true with schemas/ committed: this DB holds a medical record,
+ * so every future schema change ships as a tested Migration against the
+ * exported baseline — never destructive fallback.
+ *
+ * Enums are stored as TEXT (Room's built-in enum converter); all other columns
+ * are primitives, so no TypeConverters are needed yet.
+ */
+@Database(
+    entities = [Medication::class, DoseTime::class, DoseLog::class],
+    version = 1,
+    exportSchema = true,
+)
+abstract class MedDatabase : RoomDatabase() {
+    abstract fun medicationDao(): MedicationDao
+    abstract fun doseTimeDao(): DoseTimeDao
+    abstract fun doseLogDao(): DoseLogDao
+
+    companion object {
+        @Volatile private var instance: MedDatabase? = null
+
+        fun get(context: Context): MedDatabase =
+            instance ?: synchronized(this) {
+                instance ?: Room.databaseBuilder(
+                    context.applicationContext,
+                    MedDatabase::class.java,
+                    "med-det-samme.db",
+                ).build().also { instance = it }
+            }
+    }
+}