Initial commit — ferrosonic terminal Subsonic client

Terminal-based Subsonic music client in Rust featuring bit-perfect audio
playback via PipeWire sample rate switching, gapless playback, MPRIS2
desktop integration, cava audio visualizer with theme-matched gradients,
13 built-in color themes with custom TOML theme support, mouse controls,
artist/album browser, playlist support, and play queue management.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/subsonic/auth.rs

@@ -0,0 +1,61 @@
+//! Subsonic authentication helpers
+
+use rand::Rng;
+
+/// Generate authentication parameters for Subsonic API requests
+///
+/// Subsonic uses token-based authentication:
+/// - salt: random string
+/// - token: md5(password + salt)
+pub fn generate_auth_params(password: &str) -> (String, String) {
+    let salt = generate_salt();
+    let token = generate_token(password, &salt);
+    (salt, token)
+}
+
+/// Generate a random salt string
+fn generate_salt() -> String {
+    let mut rng = rand::thread_rng();
+    (0..16)
+        .map(|_| {
+            let idx = rng.gen_range(0..36);
+            if idx < 10 {
+                (b'0' + idx) as char
+            } else {
+                (b'a' + idx - 10) as char
+            }
+        })
+        .collect()
+}
+
+/// Generate authentication token: md5(password + salt)
+fn generate_token(password: &str, salt: &str) -> String {
+    let input = format!("{}{}", password, salt);
+    let digest = md5::compute(input.as_bytes());
+    format!("{:x}", digest)
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_generate_token() {
+        // Test with known values
+        let token = generate_token("sesame", "c19b2d");
+        assert_eq!(token, "26719a1196d2a940705a59634eb18eab");
+    }
+
+    #[test]
+    fn test_generate_salt_length() {
+        let salt = generate_salt();
+        assert_eq!(salt.len(), 16);
+    }
+
+    #[test]
+    fn test_auth_params() {
+        let (salt, token) = generate_auth_params("password");
+        assert_eq!(salt.len(), 16);
+        assert_eq!(token.len(), 32); // MD5 hex is 32 chars
+    }
+}