fix(tauri): replace silent let _ = with structured logging across 20 modules

Replace error-swallowing let _ = patterns with tracing::warn! in browser,
classroom, gateway, intelligence, memory, pipeline, secure_storage, and
viking command handlers. Ensures errors are observable in production logs.

desktop/src-tauri/src/llm/mod.rs

@@ -325,6 +325,7 @@ impl LlmClient {
 
 // === Tauri Commands ===
 
+// @reserved: 暂无前端集成
 #[tauri::command]
 pub async fn llm_complete(
     provider: String,
@@ -452,6 +453,7 @@ impl EmbeddingClient {
     }
 }
 
+// @connected
 #[tauri::command]
 pub async fn embedding_create(
     provider: String,
@@ -471,6 +473,7 @@ pub async fn embedding_create(
     client.embed(&text).await
 }
 
+// @connected
 #[tauri::command]
 pub async fn embedding_providers() -> Result<Vec<(String, String, String, usize)>, String> {
     let configs = get_embedding_provider_configs();