Refactor/simplify proxy logs (#585)

* refactor(proxy): simplify logging for better readability

- Delete 17 verbose debug logs from handlers, streaming, and response_processor
- Convert excessive INFO logs to DEBUG level for internal processing details
- Add 2 critical INFO logs in forwarder.rs for failover scenarios:
  - Log when switching to next provider after failure
  - Log when all providers have been exhausted
- Fix clippy uninlined_format_args warning

This reduces log noise while maintaining visibility into key user-facing decisions.

* fix: replace unsafe unwrap() calls with proper error handling

- database/dao/mcp.rs: Use map_err for serde_json serialization
- database/dao/providers.rs: Use map_err for settings_config and meta serialization
- commands/misc.rs: Use expect() for compile-time regex pattern
- services/prompt.rs: Use unwrap_or_default() for SystemTime
- deeplink/provider.rs: Replace unwrap() with is_none_or pattern for Option checks

Reduces potential panic points from 26 to 1 (static regex init, safe).

* refactor(proxy): simplify verbose logging output

- Remove response JSON full output logging in response_processor
- Remove per-request INFO logs in provider_router (failover status, provider selection)
- Change model mapping log from INFO to DEBUG
- Change usage logging failure from INFO to WARN
- Remove redundant debug logs for circuit breaker operations

Reduces log noise significantly while preserving important warnings and errors.

* feat(proxy): add structured log codes for i18n support

Add error code system to proxy module logs for multi-language support:

- CB-001~006: Circuit breaker state transitions and triggers
- SRV-001~004: Proxy server lifecycle events
- FWD-001~002: Request forwarding and failover
- FO-001~005: Failover switch operations
- USG-001~002: Usage logging errors

Log format: [CODE] Chinese message
Frontend/log tools can map codes to any language.

New file: src/proxy/log_codes.rs - centralized code definitions

* chore: bump version to 3.9.1

* style: format code with prettier and rustfmt

* fix(ui): allow number inputs to be fully cleared before saving

- Convert numeric state to string type for controlled inputs
- Use isNaN() check instead of || fallback to allow 0 values
- Apply fix to ProxyPanel, CircuitBreakerConfigPanel,
  AutoFailoverConfigPanel, and ModelTestConfigPanel

* feat(pricing): support @ separator in model name matching

- Refactor model name cleaning into chained method calls
- Add @ to - replacement (e.g., gpt-5.2-codex@low → gpt-5.2-codex-low)
- Add test case for @ separator matching

* fix(proxy): improve validation and error handling in proxy config panels

- Add StopTimeout/StopFailed error types for proper stop() error reporting
- Replace silent clamp with validation-and-block in config panels
- Add listenAddress format validation in ProxyPanel
- Use log_codes constants instead of hardcoded strings
- Use once_cell::Lazy for regex precompilation

* fix(proxy): harden error handling and input validation

- Handle RwLock poisoning in settings.rs with unwrap_or_else
- Add fallback for dirs::home_dir() in config modules
- Normalize localhost to 127.0.0.1 in ProxyPanel
- Format IPv6 addresses with brackets for valid URLs
- Strict port validation with pure digit regex
- Treat NaN as validation failure in config panels
- Log warning on cost_multiplier parse failure
- Align timeoutSeconds range to [0, 300] across all panels

src-tauri/src/proxy/server.rs

@@ -3,8 +3,8 @@
 //! 基于Axum的HTTP服务器，处理代理请求
 
 use super::{
-    failover_switch::FailoverSwitchManager, handlers, provider_router::ProviderRouter, types::*,
-    ProxyError,
+    failover_switch::FailoverSwitchManager, handlers, log_codes::srv as log_srv,
+    provider_router::ProviderRouter, types::*, ProxyError,
 };
 use crate::database::Database;
 use axum::{
@@ -95,7 +95,7 @@ impl ProxyServer {
             .await
             .map_err(|e| ProxyError::BindFailed(e.to_string()))?;
 
-        log::info!("代理服务器启动于 {addr}");
+        log::info!("[{}] 代理服务器启动于 {addr}", log_srv::STARTED);
 
         // 保存关闭句柄
         *self.shutdown_tx.write().await = Some(shutdown_tx);
@@ -146,13 +146,25 @@ impl ProxyServer {
         // 2. 等待服务器任务结束（带 5 秒超时保护）
         if let Some(handle) = self.server_handle.write().await.take() {
             match tokio::time::timeout(std::time::Duration::from_secs(5), handle).await {
-                Ok(Ok(())) => log::info!("代理服务器已完全停止"),
-                Ok(Err(e)) => log::warn!("代理服务器任务异常终止: {e}"),
-                Err(_) => log::warn!("代理服务器停止超时（5秒），强制继续"),
+                Ok(Ok(())) => {
+                    log::info!("[{}] 代理服务器已完全停止", log_srv::STOPPED);
+                    Ok(())
+                }
+                Ok(Err(e)) => {
+                    log::warn!("[{}] 代理服务器任务异常终止: {e}", log_srv::TASK_ERROR);
+                    Err(ProxyError::StopFailed(e.to_string()))
+                }
+                Err(_) => {
+                    log::warn!(
+                        "[{}] 代理服务器停止超时（5秒），强制继续",
+                        log_srv::STOP_TIMEOUT
+                    );
+                    Err(ProxyError::StopTimeout)
+                }
             }
+        } else {
+            Ok(())
         }
-
-        Ok(())
     }
 
     pub async fn get_status(&self) -> ProxyStatus {