Initial commit: QobuzD - Qobuz Connect renderer for Linux

Rust-based QConnect renderer with:
- QConnect WebSocket protocol (hand-rolled protobuf)
- Audio playback via Symphonia + cpal
- Play, pause, resume, volume, skip support
- Correct BufferState/PlayingState enum values per proto spec
- Server-driven queue management (no local queue)
- Periodic position reporting for track-end detection

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/config.rs

@@ -0,0 +1,102 @@
+use crate::crypto;
+use crate::error::{QobuzError, Result};
+use directories::ProjectDirs;
+use serde::{Deserialize, Serialize};
+use std::path::PathBuf;
+
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct Config {
+    pub app_id: String,
+    pub device_id: String,
+    pub session_id: String,
+    pub device_name: String,
+    pub cache_dir: PathBuf,
+    pub config_dir: PathBuf,
+    pub credentials: Option<StoredCredentials>,
+}
+
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct StoredCredentials {
+    pub access_token: String,
+    pub refresh_token: String,
+    pub user_id: Option<u64>,
+    pub expires_at: Option<i64>,
+    pub email: Option<String>,
+}
+
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct DeviceLinkCredentials {
+    pub device_access_token: String,
+    pub device_refresh_token: String,
+    pub device_id: String,
+    pub link_device_id: String,
+    pub expires_at: Option<i64>,
+}
+
+impl Config {
+    pub fn new(device_name: String) -> Result<Self> {
+        let proj_dirs = ProjectDirs::from("com", "qobuz", "qobuzd").ok_or_else(|| {
+            QobuzError::ConfigError("Could not determine config directory".into())
+        })?;
+
+        let config_dir = proj_dirs.config_dir().to_path_buf();
+        let cache_dir = proj_dirs.cache_dir().to_path_buf();
+
+        std::fs::create_dir_all(&config_dir)?;
+        std::fs::create_dir_all(&cache_dir)?;
+
+        let device_id = crypto::generate_device_id();
+        let session_id = crypto::generate_session_id();
+
+        Ok(Self {
+            app_id: "312369995".to_string(),
+            device_id,
+            session_id,
+            device_name,
+            cache_dir,
+            config_dir,
+            credentials: None,
+        })
+    }
+
+    pub fn load() -> Result<Self> {
+        let proj_dirs = ProjectDirs::from("com", "qobuz", "qobuzd").ok_or_else(|| {
+            QobuzError::ConfigError("Could not determine config directory".into())
+        })?;
+
+        let config_path = proj_dirs.config_dir().join("config.json");
+
+        if config_path.exists() {
+            let content = std::fs::read_to_string(&config_path)?;
+            let config: Config = serde_json::from_str(&content)?;
+            Ok(config)
+        } else {
+            Self::new("qobuzd".to_string())
+        }
+    }
+
+    pub fn save(&self) -> Result<()> {
+        let config_path = self.config_dir.join("config.json");
+        let content = serde_json::to_string_pretty(self)?;
+        std::fs::write(config_path, content)?;
+        Ok(())
+    }
+
+    pub fn store_credentials(&mut self, creds: StoredCredentials) -> Result<()> {
+        self.credentials = Some(creds);
+        self.save()
+    }
+
+    pub fn clear_credentials(&mut self) -> Result<()> {
+        self.credentials = None;
+        self.save()
+    }
+
+    pub fn credentials_path(&self) -> PathBuf {
+        self.config_dir.join("credentials.enc")
+    }
+
+    pub fn device_link_credentials_path(&self) -> PathBuf {
+        self.config_dir.join("device_link.json")
+    }
+}