feat: 主题切换 + 浅色模式适配，SFTP/批量命令/Webhook/仪表盘全面升级

backend/src/main/java/com/sshmanager/service/QuickConnectionRegistry.java

@@ -0,0 +1,60 @@
+package com.sshmanager.service;
+
+import com.sshmanager.entity.Connection;
+import org.springframework.stereotype.Component;
+
+import java.time.Instant;
+import java.util.Map;
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.atomic.AtomicLong;
+
+/**
+ * In-memory registry for quick-connect (ephemeral) SSH connections.
+ * Entries are NOT persisted to the database and are cleaned up
+ * when the WebSocket session closes.
+ */
+@Component
+public class QuickConnectionRegistry {
+
+    private final AtomicLong idGen = new AtomicLong(10_000_000);
+    private final Map<Long, Entry> entries = new ConcurrentHashMap<>();
+
+    public Connection create(String host, String username, int port, Long userId) {
+        long id = idGen.incrementAndGet();
+        Connection conn = new Connection();
+        conn.setId(id);
+        conn.setUserId(userId);
+        conn.setName(host + "-quick");
+        conn.setHost(host);
+        conn.setPort(port);
+        conn.setUsername(username);
+        conn.setAuthType(Connection.AuthType.PASSWORD);
+        conn.setEncryptedPassword(null);
+        conn.setCreatedAt(Instant.now());
+        conn.setUpdatedAt(Instant.now());
+        entries.put(id, new Entry(conn));
+        return conn;
+    }
+
+    public Connection get(Long id) {
+        Entry entry = entries.get(id);
+        return entry != null ? entry.connection : null;
+    }
+
+    public void remove(Long id) {
+        entries.remove(id);
+    }
+
+    public int size() {
+        return entries.size();
+    }
+
+    private static class Entry {
+        final Connection connection;
+        final long createdAt = System.currentTimeMillis();
+
+        Entry(Connection connection) {
+            this.connection = connection;
+        }
+    }
+}