theme config, layout preview, container alignment

Server: ThemeConfig entity + CRUD (GET/PUT /theme), SQLite persistence,
ThemeUpdate broadcast to ESP32 on save and initial connect.
Client: render engine uses theme colors, full-screen redraw on theme change.
SPA: theme page with color pickers + presets, layout preview with TS port
of layout engine, justify/align controls on containers.
DisplayHint refactored to struct (kind + h_align + v_align).

crates/adapters/config-sqlite/src/lib.rs

@@ -87,6 +87,15 @@ impl SqliteConfigStore {
         .execute(&self.pool)
         .await?;
 
+        sqlx::query(
+            "CREATE TABLE IF NOT EXISTS theme (
+                id INTEGER PRIMARY KEY CHECK (id = 1),
+                data TEXT NOT NULL
+            )",
+        )
+        .execute(&self.pool)
+        .await?;
+
         Ok(())
     }
 }