refactor adapters into modular file structure

config-sqlite: split into repository/ (per entity) + serialization/ (per type) + error.rs
http-api: split into dto/ (per resource) + routes/ (per resource)
tcp-server: split into broadcaster, event_bus, server, error
rss: split parser from adapter, external tests
media: split error, external tests

crates/adapters/config-sqlite/src/repository/widgets.rs

@@ -0,0 +1,58 @@
+use domain::{WidgetConfig, WidgetId};
+use crate::SqliteConfigStore;
+use crate::error::SqliteConfigError;
+use crate::serialization::widget as ser;
+
+impl SqliteConfigStore {
+    pub(crate) async fn get_widget_impl(&self, id: WidgetId) -> Result<Option<WidgetConfig>, SqliteConfigError> {
+        let row = sqlx::query("SELECT * FROM widgets WHERE id = ?")
+            .bind(id as i64)
+            .fetch_optional(&self.pool)
+            .await
+            .map_err(SqliteConfigError::Sql)?;
+
+        match row {
+            None => Ok(None),
+            Some(row) => Ok(Some(ser::widget_from_row(&row)?)),
+        }
+    }
+
+    pub(crate) async fn list_widgets_impl(&self) -> Result<Vec<WidgetConfig>, SqliteConfigError> {
+        let rows = sqlx::query("SELECT * FROM widgets")
+            .fetch_all(&self.pool)
+            .await
+            .map_err(SqliteConfigError::Sql)?;
+
+        rows.iter().map(|r| ser::widget_from_row(r)).collect()
+    }
+
+    pub(crate) async fn save_widget_impl(&self, config: &WidgetConfig) -> Result<(), SqliteConfigError> {
+        let mappings_json = ser::mappings_to_json(&config.mappings)?;
+        let hint_str = ser::display_hint_to_str(&config.display_hint);
+
+        sqlx::query(
+            "INSERT OR REPLACE INTO widgets (id, name, display_hint, data_source_id, mappings, max_data_size)
+             VALUES (?, ?, ?, ?, ?, ?)"
+        )
+        .bind(config.id as i64)
+        .bind(&config.name)
+        .bind(hint_str)
+        .bind(config.data_source_id as i64)
+        .bind(&mappings_json)
+        .bind(config.max_data_size as i64)
+        .execute(&self.pool)
+        .await
+        .map_err(SqliteConfigError::Sql)?;
+
+        Ok(())
+    }
+
+    pub(crate) async fn delete_widget_impl(&self, id: WidgetId) -> Result<(), SqliteConfigError> {
+        sqlx::query("DELETE FROM widgets WHERE id = ?")
+            .bind(id as i64)
+            .execute(&self.pool)
+            .await
+            .map_err(SqliteConfigError::Sql)?;
+        Ok(())
+    }
+}