feat(rustdesk): 优化视频编码协商和添加公共服务器支持

- 调整视频编码优先级为 H264 > H265 > VP8 > VP9，优先使用硬件编码
- 对接 RustDesk 客户端质量预设 (Low/Balanced/Best) 到 BitratePreset
- 添加 secrets.toml 编译时读取机制，支持配置公共服务器
- 默认公共服务器: rustdesk.mofeng.run:21116
- 前端 ID 服务器输入框添加问号提示，显示公共服务器信息
- 用户留空时自动使用公共服务器

build.rs

@@ -1,3 +1,6 @@
+use std::fs;
+use std::path::Path;
+
 fn main() {
     // Set BUILD_DATE environment variable for compile-time access
     // Use system time to avoid adding chrono as a build dependency
@@ -17,10 +20,14 @@ fn main() {
     // Compile protobuf files for RustDesk protocol
     compile_protos();
 
+    // Generate secrets module from secrets.toml
+    generate_secrets();
+
     // Rerun if the script itself changes
     println!("cargo:rerun-if-changed=build.rs");
     println!("cargo:rerun-if-changed=protos/rendezvous.proto");
     println!("cargo:rerun-if-changed=protos/message.proto");
+    println!("cargo:rerun-if-changed=secrets.toml");
 }
 
 /// Compile protobuf files using prost-build
@@ -36,6 +43,104 @@ fn compile_protos() {
         .expect("Failed to compile protobuf files");
 }
 
+/// Generate secrets module from secrets.toml
+///
+/// This reads the secrets.toml file and generates a Rust module with
+/// compile-time constants for sensitive configuration values.
+fn generate_secrets() {
+    let out_dir = std::env::var("OUT_DIR").unwrap();
+    let dest_path = Path::new(&out_dir).join("secrets_generated.rs");
+
+    // Default values if secrets.toml doesn't exist
+    let mut rustdesk_public_server = String::new();
+    let mut rustdesk_public_key = String::new();
+    let mut turn_server = String::new();
+    let mut turn_username = String::new();
+    let mut turn_password = String::new();
+
+    // Try to read secrets.toml
+    if let Ok(content) = fs::read_to_string("secrets.toml") {
+        if let Ok(value) = content.parse::<toml::Value>() {
+            // RustDesk section
+            if let Some(rustdesk) = value.get("rustdesk") {
+                if let Some(v) = rustdesk.get("public_server").and_then(|v| v.as_str()) {
+                    rustdesk_public_server = v.to_string();
+                }
+                if let Some(v) = rustdesk.get("public_key").and_then(|v| v.as_str()) {
+                    rustdesk_public_key = v.to_string();
+                }
+            }
+
+            // TURN section (for future use)
+            if let Some(turn) = value.get("turn") {
+                if let Some(v) = turn.get("server").and_then(|v| v.as_str()) {
+                    turn_server = v.to_string();
+                }
+                if let Some(v) = turn.get("username").and_then(|v| v.as_str()) {
+                    turn_username = v.to_string();
+                }
+                if let Some(v) = turn.get("password").and_then(|v| v.as_str()) {
+                    turn_password = v.to_string();
+                }
+            }
+        } else {
+            println!("cargo:warning=Failed to parse secrets.toml");
+        }
+    } else {
+        println!("cargo:warning=secrets.toml not found, using empty defaults");
+    }
+
+    // Generate the secrets module
+    let code = format!(
+        r#"// Auto-generated secrets module
+// DO NOT EDIT - This file is generated by build.rs from secrets.toml
+
+/// RustDesk public server configuration
+pub mod rustdesk {{
+    /// Public RustDesk ID server address (used when user leaves field empty)
+    pub const PUBLIC_SERVER: &str = "{}";
+
+    /// Public key for the RustDesk server (for client connection)
+    pub const PUBLIC_KEY: &str = "{}";
+
+    /// Check if public server is configured
+    pub const fn has_public_server() -> bool {{
+        !PUBLIC_SERVER.is_empty()
+    }}
+}}
+
+/// TURN server configuration (for WebRTC)
+pub mod turn {{
+    /// TURN server address
+    pub const SERVER: &str = "{}";
+
+    /// TURN username
+    pub const USERNAME: &str = "{}";
+
+    /// TURN password
+    pub const PASSWORD: &str = "{}";
+
+    /// Check if TURN server is configured
+    pub const fn is_configured() -> bool {{
+        !SERVER.is_empty()
+    }}
+}}
+"#,
+        escape_string(&rustdesk_public_server),
+        escape_string(&rustdesk_public_key),
+        escape_string(&turn_server),
+        escape_string(&turn_username),
+        escape_string(&turn_password),
+    );
+
+    fs::write(&dest_path, code).expect("Failed to write secrets_generated.rs");
+}
+
+/// Escape special characters in a string for use in Rust string literals
+fn escape_string(s: &str) -> String {
+    s.replace('\\', "\\\\").replace('"', "\\\"")
+}
+
 /// Convert days since Unix epoch to year-month-day
 fn days_to_ymd(days: i64) -> (i32, u32, u32) {
     // Algorithm from http://howardhinnant.github.io/date_algorithms.html