feat(nightlight): geo mode — lat/long-computed sunset via wlsunset

Set BOTH nomarchy.nightlight.latitude/.longitude and the night light
switches backing unit: wlsunset computes sunrise/sunset from the
location daily (the fixed .sunrise/.sunset are ignored;
.temperature feeds the night temp). Everything user-facing is
unchanged — same nomarchy-nightlight toggle script, Waybar moon, and
live-state ExecCondition gate; the unit name is a single let-binding
so all three follow together. Declarative-only on purpose: coordinates
are machine config like the keyboard layout, so home.nix (commented
template example), not a menu writer.

checks.nightlight-geo guards the wiring at pure eval: rendered
wlsunset ExecStart carries the coords + night temperature, the
ExecCondition gate landed on the swapped unit, hyprsunset stays off in
geo mode.

Verification: V1 — nix flake check --no-build exit 0 (evals the new
asserts + option-docs sync); built downstream-template-home (default
hyprsunset path unregressed). V3 pending: visible warm shift at the
location's night + instant toggle/off-persistence on the swapped unit
(HARDWARE-QUEUE § Any machine).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

modules/home/options.nix

@@ -192,8 +192,9 @@ in
 
     nightlight = {
       enable = lib.mkEnableOption ''
-        a scheduled blue-light filter (hyprsunset): warm at night, no shift
-        by day. Opt-in; tune the temperature + sunrise/sunset below'';
+        a scheduled blue-light filter (hyprsunset; wlsunset in geo mode):
+        warm at night, no shift by day. Opt-in; tune the temperature +
+        sunrise/sunset (or latitude/longitude) below'';
 
       temperature = lib.mkOption {
         type = lib.types.int;
@@ -206,14 +207,31 @@ in
         type = lib.types.str;
         default = "07:00";
         example = "06:30";
-        description = "Time (HH:MM) the filter turns OFF — daytime, no colour shift.";
+        description = "Time (HH:MM) the filter turns OFF — daytime, no colour shift. Ignored in geo mode.";
       };
 
       sunset = lib.mkOption {
         type = lib.types.str;
         default = "20:00";
         example = "21:00";
-        description = "Time (HH:MM) the filter turns ON — warm.";
+        description = "Time (HH:MM) the filter turns ON — warm. Ignored in geo mode.";
+      };
+
+      latitude = lib.mkOption {
+        type = lib.types.nullOr lib.types.str;
+        default = null;
+        example = "52.52";
+        description = ''
+          Geo mode: set BOTH latitude and longitude and sunrise/sunset are
+          computed from your location every day (wlsunset replaces
+          hyprsunset; the fixed .sunrise/.sunset times are ignored).'';
+      };
+
+      longitude = lib.mkOption {
+        type = lib.types.nullOr lib.types.str;
+        default = null;
+        example = "13.40";
+        description = "Geo mode longitude — set together with latitude.";
       };
     };