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/rss/src/error.rs

@@ -0,0 +1,16 @@
+#[derive(Debug)]
+pub enum RssError {
+    Request(reqwest::Error),
+    NoUrl,
+    Parse(String),
+}
+
+impl std::fmt::Display for RssError {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match self {
+            RssError::Request(e) => write!(f, "request: {e}"),
+            RssError::NoUrl => write!(f, "no url configured"),
+            RssError::Parse(e) => write!(f, "parse: {e}"),
+        }
+    }
+}