Add a Locus Pro-style toolbar readout: DMS coords + sunrise/sunset

The topbar's coordinate display was plain decimal degrees ("48.14611,
17.17722") — switched to DMS (48°08'46"N 17°10'38"E), the more
GPS-unit-like format Locus Pro itself uses, and made it click-to-copy
(plain decimal, since that's what pastes cleanly into another map/GPS
app — not the DMS text actually shown).

Added sunrise/sunset + a countdown to whichever's next, for the same
map-center point the coordinates already describe. Vendored SunCalc
(BSD-2-Clause, github.com/mourner/suncalc) rather than hand-rolling
the astronomical math — small, dependency-free, and correctness here
has real pitfalls (equation of time, refraction, polar day/night) a
first-pass reimplementation would risk getting subtly wrong.

Also added a test asserting every public/js/*.js module has a
versioned importmap entry in layout.erb — caught that overlays.js
(from the previous commit) was missing one, which would have quietly
skipped ASSET_VERSION's cache-busting for that file after every
deploy.

public/js/map.js

@@ -15,6 +15,7 @@ import { NotesControl } from "/js/notes.js";
 import { PluginsControl } from "/js/plugins.js";
 import { LocateControl } from "/js/locate.js";
 import { LAYERS_ICON, HILLSHADE_ICON } from "/js/icons.js";
+import { formatCoords, formatSunInfo } from "/js/sun.js";
 import { notifySidePanelOpen, onlyOneSidePanelOpen } from "/js/panels.js";
 import { isLoggedIn } from "/js/auth.js";
 import HomeButton from "/vendor/npmap-home-button/home-button.esm.js";
@@ -540,11 +541,42 @@ map.once("style.load", () => {
 const coordsLabel = document.querySelector(".topbar__coords");
 const updateCoords = () => {
   const { lng, lat } = map.getCenter();
-  coordsLabel.textContent = `${lat.toFixed(5)}, ${lng.toFixed(5)}`;
+  coordsLabel.textContent = formatCoords(lat, lng);
 };
 updateCoords();
 map.on("move", updateCoords);
 
+// Plain decimal degrees, not the DMS text actually shown — that's what
+// pastes cleanly into another map/GPS app, which is the whole point of
+// copying a coordinate in the first place.
+coordsLabel.title = "Click to copy coordinates";
+coordsLabel.addEventListener("click", async () => {
+  const { lng, lat } = map.getCenter();
+  try {
+    await navigator.clipboard.writeText(`${lat.toFixed(6)}, ${lng.toFixed(6)}`);
+  } catch {
+    return; // clipboard API unavailable (e.g. an insecure context) — nothing to fall back to
+  }
+  coordsLabel.textContent = "Copied!";
+  setTimeout(updateCoords, 1000);
+});
+
+// Sunrise/sunset for the same center point the coords above already show —
+// on moveend (not every "move" frame, unlike updateCoords: the sun position
+// barely moves between two nearby spots, not worth recomputing constantly)
+// plus a periodic tick so the "Xh Ym to sunset" countdown keeps counting
+// down even while the map sits still.
+const sunLabel = document.querySelector(".topbar__sun");
+const updateSun = () => {
+  const { lng, lat } = map.getCenter();
+  const info = formatSunInfo(lat, lng);
+  sunLabel.textContent = info ?? "";
+  sunLabel.hidden = info === null;
+};
+updateSun();
+map.on("moveend", updateSun);
+setInterval(updateSun, 60000);
+
 const sidebar = document.getElementById("sidebar");
 
 // Grouped into the TODO's planned 4-module menu (Explorer / Offline hub /