state recovery, polling optimizations, error rendering

widget states cached to SQLite, loaded on startup to seed DataProjection
so server restart preserves last-known data for reconnecting clients.

polling: first poll runs immediately, widget list cached per-task with
30s refresh, static text polled once inline instead of looping.

poll failures propagate WidgetError::SourceUnavailable to clients.
render engine prepends [offline] prefix in accent color, stale data
preserved below.

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

@@ -96,6 +96,15 @@ impl SqliteConfigStore {
         .execute(&self.pool)
         .await?;
 
+        sqlx::query(
+            "CREATE TABLE IF NOT EXISTS widget_state_cache (
+                widget_id INTEGER PRIMARY KEY,
+                state_json TEXT NOT NULL
+            )",
+        )
+        .execute(&self.pool)
+        .await?;
+
         // Add alignment columns to widgets (idempotent)
         let _ = sqlx::query("ALTER TABLE widgets ADD COLUMN h_align TEXT NOT NULL DEFAULT 'left'")
             .execute(&self.pool)