Add `submit_on_click` to trigger unlock from pointer/touch

[J-Melon]

Problem

hyprlock requires a physical Return keypress to submit the password. There is no pointer or touch path to submit.

Submission goes through g_pAuth->submitInput(passBuffer), currently only reached from the XKB_KEY_Return / XKB_KEY_KP_Enter branch in src/core/hyprlock.cpp.

Current workaround is synthesising Return via ydotool, which needs uinput and ydotoold.

Proposed shape

A boolean submit_on_click on the clickable widgets (label, image, shape) that already carry onclick from #736. When the widget is clicked and the option is set, hyprlock calls submitInput on the current buffer.

shape {
    size = 200, 60
    position = 0, -100
    halign = center
    valign = center
    submit_on_click = true
}

Parallels fade_on_empty, ignore_empty_input etc. for naming.

Semantics

• Honours general:ignore_empty_input identically to the Return branch.
• Must gate on g_pAuth->checkWaiting() to match the existing guard at src/core/hyprlock.cpp:617, which short-circuits the Return path while PAM is mid-check. The widget click path has no such guard today, so rapid clicking would otherwise queue concurrent submitInput calls.
• If both onclick and submit_on_click are set on the same widget, the shell command is spawned asynchronously and submitInput is called in the same handler; order between the async spawn and the PAM call is not observable.

Notes

• Related: Support touch with hide_cursor #854 (touch with hide_cursor).