feat(model-test): add provider model availability testing

Implement standalone model testing feature to verify provider API connectivity:
- Add ModelTestService for Claude/Codex/Gemini endpoint testing
- Create model_test_logs table for test result persistence
- Add test button to ProviderCard with loading state
- Include ModelTestConfigPanel for customizing test parameters

src-tauri/src/database/schema.rs

@@ -303,6 +303,39 @@ impl Database {
         )
         .map_err(|e| AppError::Database(e.to_string()))?;
 
+        // 14. Model Test Logs 表 (模型测试日志，独立于代理使用统计)
+        conn.execute(
+            "CREATE TABLE IF NOT EXISTS model_test_logs (
+                id INTEGER PRIMARY KEY AUTOINCREMENT,
+                provider_id TEXT NOT NULL,
+                provider_name TEXT NOT NULL,
+                app_type TEXT NOT NULL,
+                model TEXT NOT NULL,
+                prompt TEXT NOT NULL,
+                success INTEGER NOT NULL,
+                message TEXT NOT NULL,
+                response_time_ms INTEGER,
+                http_status INTEGER,
+                tested_at INTEGER NOT NULL
+            )",
+            [],
+        )
+        .map_err(|e| AppError::Database(e.to_string()))?;
+
+        conn.execute(
+            "CREATE INDEX IF NOT EXISTS idx_model_test_logs_provider
+             ON model_test_logs(provider_id, app_type)",
+            [],
+        )
+        .map_err(|e| AppError::Database(e.to_string()))?;
+
+        conn.execute(
+            "CREATE INDEX IF NOT EXISTS idx_model_test_logs_tested_at
+             ON model_test_logs(tested_at DESC)",
+            [],
+        )
+        .map_err(|e| AppError::Database(e.to_string()))?;
+
         Ok(())
     }