refactor: power-confirm via PowerAction table (v0.6.14)

Align the power-confirm flow to moonset's ActionDef pattern, in lockstep
with moongreet: a PowerAction table + create_power_button factory replace
the two hand-wired reboot/shutdown handlers and the loose-param
show_power_confirm. Add an in-flight re-trigger guard
(power_box.set_sensitive(false)) and clear a stale error_label when
showing a new prompt.

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "moonlock"
-version = "0.6.13"
+version = "0.6.14"
 edition = "2024"
 description = "A secure Wayland lockscreen with GTK4, PAM and fingerprint support"
 license = "MIT"
@@ -28,6 +28,7 @@ tempfile = "3"
 glib-build-tools = "0.22"
 
 [profile.release]
-lto = "fat"
+lto = "thin"
 codegen-units = 1
-strip = true
+strip = false
+debug = true