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/tcp-server/src/error.rs

@@ -0,0 +1,14 @@
+#[derive(Debug)]
+pub enum TcpServerError {
+    Io(std::io::Error),
+    Encode(postcard::Error),
+}
+
+impl std::fmt::Display for TcpServerError {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match self {
+            TcpServerError::Io(e) => write!(f, "io: {e}"),
+            TcpServerError::Encode(e) => write!(f, "encode: {e}"),
+        }
+    }
+}