feat: initial x3-ssh client

- GTK3 GUI with VTE terminal emulation
- Tabbed SSH sessions
- Server management (add/edit/remove)
- SSH key management (generate/import/delete)
- Quick connect bar
- libssh for SSH connections
- autotools build system (configure && make)

src/ssh_terminal.h

@@ -0,0 +1,39 @@
+#pragma once
+#include <gtk/gtk.h>
+#include <vte/vte.h>
+#include <libssh/libssh.h>
+#include <atomic>
+#include <string>
+#include <functional>
+
+class SshTerminal {
+public:
+	SshTerminal();
+	~SshTerminal();
+
+	bool connect(const std::string& host, int port, const std::string& user,
+	             const std::string& keyfile, const std::string& password);
+	void disconnect();
+	bool is_connected() const { return connected_; }
+	GtkWidget* widget() const { return GTK_WIDGET(vte_box_); }
+	const std::string& server_name() const { return server_name_; }
+	void set_server_name(const std::string& name) { server_name_ = name; }
+
+	std::function<void(bool, const std::string&)> on_status_change;
+
+private:
+	void cleanup();
+	static gpointer io_thread_func(gpointer data);
+	static void on_size_changed(VteTerminal* term, guint cols, guint rows, gpointer data);
+
+	GtkWidget* vte_box_;
+	VteTerminal* terminal_;
+	ssh_session session_;
+	ssh_channel channel_;
+	int pty_master_;
+	int pty_slave_;
+	std::atomic<bool> running_;
+	std::atomic<bool> connected_;
+	GThread* thread_;
+	std::string server_name_;
+};