feat: multiple shared directories

Shares::scan_many merges several roots into one index, suffixing
duplicate root names so virtual paths cannot collide, and skipping
unreadable roots instead of failing. ClientSettings now takes
shared_directories: Vec<String>; config gains a shared_dirs list
(combined with the single shared_dir and --shared-dir, deduped), with an
explicitly empty value still disabling sharing and the
share-what-you-download default unchanged.

soulseek-rs-lib/src/client/mod.rs

@@ -97,9 +97,9 @@ pub struct ClientSettings {
     pub server_address: PeerAddress,
     pub enable_listen: bool,
     pub listen_port: u16,
-    /// Directory whose files are shared with (uploaded to) other peers.
-    /// `None` means nothing is shared.
-    pub shared_directory: Option<String>,
+    /// Directories whose files are shared with (uploaded to) other peers.
+    /// Empty means nothing is shared.
+    pub shared_directories: Vec<String>,
 }
 
 impl ClientSettings {
@@ -126,7 +126,7 @@ impl Default for ClientSettings {
             ),
             enable_listen: true,
             listen_port: DEFAULT_LISTEN_PORT,
-            shared_directory: None,
+            shared_directories: Vec::new(),
         }
     }
 }
@@ -617,7 +617,7 @@ pub struct Client {
     address: PeerAddress,
     username: String,
     password: String,
-    shared_directory: Option<String>,
+    shared_directories: Vec<String>,
     server_handle: Option<ActorHandle<ServerMessage>>,
     context: Arc<RwLock<ClientContext>>,
 }
@@ -639,16 +639,16 @@ impl Client {
             address: settings.server_address,
             username: settings.username,
             password: settings.password,
-            shared_directory: settings.shared_directory,
+            shared_directories: settings.shared_directories,
             context: Arc::new(RwLock::new(ClientContext::new())),
             server_handle: None,
         }
     }
 
-    /// The directory whose files are shared with other peers, if configured.
+    /// The directories whose files are shared with other peers.
     #[must_use]
-    pub fn shared_directory(&self) -> Option<&str> {
-        self.shared_directory.as_deref()
+    pub fn shared_directories(&self) -> &[String] {
+        &self.shared_directories
     }
 }