feat(domain): add TabFetcherPort and TabParserPort traits

crates/domain/src/ports.rs

@@ -0,0 +1,37 @@
+use std::path::PathBuf;
+use thiserror::Error;
+use async_trait::async_trait;
+use crate::song::Song;
+
+#[derive(Debug, Clone)]
+pub enum TabSource {
+    File(PathBuf),
+    Url(String),
+}
+
+#[derive(Debug, Error)]
+pub enum FetchError {
+    #[error("IO error: {0}")]
+    Io(#[from] std::io::Error),
+    #[error("Network error: {0}")]
+    Network(String),
+    #[error("Response is not HTML")]
+    InvalidContentType,
+}
+
+#[derive(Debug, Error)]
+pub enum ParseError {
+    #[error("Tab content not found in HTML")]
+    MissingContent,
+    #[error("Malformed HTML: {0}")]
+    MalformedHtml(String),
+}
+
+#[async_trait]
+pub trait TabFetcherPort: Send + Sync {
+    async fn fetch(&self, source: TabSource) -> Result<String, FetchError>;
+}
+
+pub trait TabParserPort: Send + Sync {
+    fn parse(&self, html: &str) -> Result<Song, ParseError>;
+}