Add SQLite persistence via Docker named volume

Tasks are now stored in SQLite (DB_PATH env var, defaults to ./tasks.db).
Pre-seeding runs only when the table is empty, so upgrades preserve data.
This is the v1.0.0 baseline for the persistence demo.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/main/scala/TaskStore.scala

@@ -1,41 +1,87 @@
 import java.util.UUID
-import java.util.concurrent.ConcurrentHashMap
-import scala.jdk.CollectionConverters.*
+import java.sql.{Connection, DriverManager}
 
 case class Task(id: UUID, title: String, completed: Boolean)
 
 object TaskStore:
-  private val tasks = ConcurrentHashMap[UUID, Task]()
+  private val dbPath = sys.env.getOrElse("DB_PATH", "./tasks.db")
+  private val url = s"jdbc:sqlite:$dbPath"
 
-  // Pre-seed sample tasks
+  Class.forName("org.sqlite.JDBC")
+
+  private def connect(): Connection = DriverManager.getConnection(url)
+
+  // Initialize schema and pre-seed if empty
   locally {
-    val samples = List(
-      "Deploy Scala app to Clouderized",
-      "Set up CI/CD with Gitea Actions",
-      "Configure custom domain"
-    )
-    samples.foreach { title =>
-      val id = UUID.randomUUID()
-      tasks.put(id, Task(id, title, false))
-    }
+    val conn = connect()
+    try
+      val stmt = conn.createStatement()
+      stmt.execute(
+        "CREATE TABLE IF NOT EXISTS tasks (id TEXT PRIMARY KEY, title TEXT NOT NULL, completed INTEGER NOT NULL DEFAULT 0)"
+      )
+      val rs = stmt.executeQuery("SELECT COUNT(*) FROM tasks")
+      val count = rs.getInt(1)
+      if count == 0 then
+        val samples = List(
+          "Deploy Scala app to Clouderized",
+          "Set up CI/CD with Gitea Actions",
+          "Configure custom domain"
+        )
+        val ps = conn.prepareStatement("INSERT INTO tasks (id, title, completed) VALUES (?, ?, 0)")
+        samples.foreach { title =>
+          ps.setString(1, UUID.randomUUID().toString)
+          ps.setString(2, title)
+          ps.executeUpdate()
+        }
+    finally conn.close()
   }
 
   def all(): List[Task] =
-    tasks.values().asScala.toList.sortBy(_.title)
+    val conn = connect()
+    try
+      val rs = conn.createStatement().executeQuery("SELECT id, title, completed FROM tasks ORDER BY title")
+      val buf = collection.mutable.ListBuffer.empty[Task]
+      while rs.next() do
+        buf += Task(UUID.fromString(rs.getString("id")), rs.getString("title"), rs.getInt("completed") == 1)
+      buf.toList
+    finally conn.close()
 
   def add(title: String): Task =
     val id = UUID.randomUUID()
-    val task = Task(id, title.trim, false)
-    tasks.put(id, task)
-    task
+    val conn = connect()
+    try
+      val ps = conn.prepareStatement("INSERT INTO tasks (id, title, completed) VALUES (?, ?, 0)")
+      ps.setString(1, id.toString)
+      ps.setString(2, title.trim)
+      ps.executeUpdate()
+      Task(id, title.trim, false)
+    finally conn.close()
 
   def toggle(id: UUID): Unit =
-    Option(tasks.get(id)).foreach { task =>
-      tasks.put(id, task.copy(completed = !task.completed))
-    }
+    val conn = connect()
+    try
+      val ps = conn.prepareStatement(
+        "UPDATE tasks SET completed = CASE WHEN completed = 1 THEN 0 ELSE 1 END WHERE id = ?"
+      )
+      ps.setString(1, id.toString)
+      ps.executeUpdate()
+    finally conn.close()
 
   def delete(id: UUID): Unit =
-    tasks.remove(id)
+    val conn = connect()
+    try
+      val ps = conn.prepareStatement("DELETE FROM tasks WHERE id = ?")
+      ps.setString(1, id.toString)
+      ps.executeUpdate()
+    finally conn.close()
 
   def get(id: UUID): Option[Task] =
-    Option(tasks.get(id))
+    val conn = connect()
+    try
+      val ps = conn.prepareStatement("SELECT id, title, completed FROM tasks WHERE id = ?")
+      ps.setString(1, id.toString)
+      val rs = ps.executeQuery()
+      if rs.next() then
+        Some(Task(UUID.fromString(rs.getString("id")), rs.getString("title"), rs.getInt("completed") == 1))
+      else None
+    finally conn.close()