ctypes auto-converts c_char_p return values to Python bytes, losing
the original malloc'd pointer from strdup(). When PAM called free()
on the response, it hit a ctypes-internal buffer instead — segfault.
Use c_void_p for PamResponse.resp and strdup restype to preserve raw
pointers. Also use calloc/strdup for proper malloc'd memory that PAM
can safely free().
Add try/except in auth thread so UI stays interactive on PAM errors.
- Use property setter for PasswordEntry placeholder text
- Remove unsupported max-width/max-height from CSS
- Set avatar size via set_size_request()
- Auto re-exec with LD_PRELOAD for gtk4-layer-shell linking order
Lockscreen window with avatar, password entry, fingerprint indicator,
power buttons. Session locking via Gtk4SessionLock (ext-session-lock-v1)
with multi-monitor support and dev fallback mode.
