feat(Auth): Unify shared PAM sync across greeter & lockscreen

- Add a neutral `dms auth sync` command and reuse the shared auth flow from:
- Settings auth toggle auto-apply
- `dms greeter sync`
- `dms greeter install`
- greeter auth cleanup paths

- Rework lockscreen PAM so DMS builds /etc/pam.d/dankshell from the system login stack, but removes fingerprint and U2F from that password path. Keep /etc/pam.d/dankshell-u2f separate.

- Preserve custom PAM files in place to avoid adding duplicate greeter auth when the distro already provides it, and keep NixOS on the non-writing path.

quickshell/Common/settings/SettingsSpec.js

@@ -169,8 +169,8 @@ var SPEC = {
     lockDateFormat: { def: "" },
     greeterRememberLastSession: { def: true },
     greeterRememberLastUser: { def: true },
-    greeterEnableFprint: { def: false },
-    greeterEnableU2f: { def: false },
+    greeterEnableFprint: { def: false, onChange: "scheduleAuthApply" },
+    greeterEnableU2f: { def: false, onChange: "scheduleAuthApply" },
     greeterWallpaperPath: { def: "" },
     greeterUse24HourClock: { def: true },
     greeterShowSeconds: { def: false },
@@ -353,7 +353,7 @@ var SPEC = {
     lockScreenShowMediaPlayer: { def: true },
     lockScreenPowerOffMonitorsOnLock: { def: false },
     lockAtStartup: { def: false },
-    enableFprint: { def: false },
+    enableFprint: { def: false, onChange: "scheduleAuthApply" },
     maxFprintTries: { def: 15 },
     fprintdAvailable: { def: false, persist: false },
     lockFingerprintCanEnable: { def: false, persist: false },
@@ -363,7 +363,7 @@ var SPEC = {
     greeterFingerprintReady: { def: false, persist: false },
     greeterFingerprintReason: { def: "probe_failed", persist: false },
     greeterFingerprintSource: { def: "none", persist: false },
-    enableU2f: { def: false },
+    enableU2f: { def: false, onChange: "scheduleAuthApply" },
     u2fMode: { def: "or" },
     u2fAvailable: { def: false, persist: false },
     lockU2fCanEnable: { def: false, persist: false },