feat: advance local-first conflict and search indexing

- 补齐本地 markdown 冲突处理与合并写回路径\n- 增加本地搜索索引路由、刷新与 browser smoke\n- 同步更新 current-priority checklist 的阶段进度

rust/crates/mnote-web/src/error.rs

@@ -4,6 +4,7 @@ use axum::http::{HeaderName, HeaderValue};
 use axum::response::{IntoResponse, Response};
 use axum::Json;
 use serde::Serialize;
+use serde_json::Value;
 
 #[derive(Debug, Clone, Serialize)]
 #[serde(rename_all = "camelCase")]
@@ -13,6 +14,8 @@ pub struct ErrorBody {
     pub message: String,
     pub request_id: Option<String>,
     pub trace_id: Option<String>,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub details: Option<Value>,
 }
 
 #[derive(Debug, Clone)]
@@ -22,6 +25,7 @@ pub struct WebError {
     message: String,
     request_context: Option<RequestContext>,
     headers: Vec<(&'static str, String)>,
+    details: Option<Value>,
 }
 
 impl WebError {
@@ -32,6 +36,7 @@ impl WebError {
             message: message.into(),
             request_context: None,
             headers: Vec::new(),
+            details: None,
         }
     }
 
@@ -69,6 +74,11 @@ impl WebError {
         self
     }
 
+    pub fn with_details(mut self, details: Value) -> Self {
+        self.details = Some(details);
+        self
+    }
+
     pub fn message(&self) -> &str {
         &self.message
     }
@@ -96,6 +106,7 @@ impl IntoResponse for WebError {
                 .request_context
                 .as_ref()
                 .map(|context| context.trace.trace_id.clone()),
+            details: self.details,
         };
         let mut response = (self.status, Json(body)).into_response();
         if let Ok(name) = HeaderName::from_lowercase(b"x-error-code") {