fix(usage): deduplicate proxy and session log usage records

Extract message_id from Claude API responses (msg_xxx) and use it to
generate a shared request_id format (session:{msg_xxx}) between the
proxy logger and session log sync. When session sync encounters the
same request_id via INSERT OR IGNORE, it skips the duplicate.

- Add message_id field to TokenUsage, extracted from Claude responses
- Add TokenUsage::dedup_request_id() to generate shared request IDs
- Define SESSION_REQUEST_ID_PREFIX constant to eliminate magic strings
- Change proxy logger to INSERT OR REPLACE for richer-data-wins semantics

src-tauri/src/proxy/response_processor.rs

@@ -528,7 +528,7 @@ async fn log_usage_internal(
         model
     };
 
-    let request_id = uuid::Uuid::new_v4().to_string();
+    let request_id = usage.dedup_request_id();
 
     log::debug!(
         "[{app_type}] 记录请求日志: id={request_id}, provider={provider_id}, model={model}, streaming={is_streaming}, status={status_code}, latency_ms={latency_ms}, first_token_ms={first_token_ms:?}, session={}, input={}, output={}, cache_read={}, cache_creation={}",
@@ -784,6 +784,7 @@ mod tests {
             cache_read_tokens: 0,
             cache_creation_tokens: 0,
             model: None,
+            message_id: None,
         };
 
         log_usage_internal(
@@ -843,6 +844,7 @@ mod tests {
             cache_read_tokens: 0,
             cache_creation_tokens: 0,
             model: None,
+            message_id: None,
         };
 
         log_usage_internal(