fix(butler): wire verification gaps — pain storage init, cold start, UI mode switches

- Call init_pain_storage() in Tauri .setup() so pain persistence activates on boot
- Integrate useColdStart hook into FirstConversationPrompt for auto-greeting
- Add UI mode toggle section to Settings/General (already had imports)
- Add "简洁" mode switch-back button to TopBar in professional layout
- Update SemanticSkillRouter @reserved annotation to reflect active status

desktop/src-tauri/src/lib.rs

@@ -155,6 +155,25 @@ pub fn run() {
                     .expect("In-memory SQLite should never fail")
             });
             app.manage(persistence);
+
+            // Initialize pain point persistence (SQLite-backed).
+            // Must complete before event loop starts so that pain aggregator
+            // has a valid storage layer for dual-write operations.
+            {
+                let app_dir = app.path().app_data_dir().expect("Failed to get app data dir");
+                let pain_db_dir = app_dir.join("intelligence");
+                std::fs::create_dir_all(&pain_db_dir).expect("Failed to create intelligence dir");
+
+                let db_path = pain_db_dir.join("pain.db");
+                let db_url = format!("sqlite:{}", db_path.display());
+                let pool = rt.block_on(sqlx::SqlitePool::connect(&db_url))
+                    .expect("Failed to connect pain storage SQLite pool");
+
+                if let Err(e) = rt.block_on(intelligence::pain_aggregator::init_pain_storage(pool)) {
+                    tracing::error!("[PainStorage] Init failed: {}, pain points will not persist", e);
+                }
+            }
+
             Ok(())
         })
         .invoke_handler(tauri::generate_handler![