refactor(calendar): stack layout, wider grid, fixed cell height

- Calendar widget stays stacked (calendar above events list)
- Grid widens to max-w-2xl with fixed h-10 cells (no aspect-square height growth)
- Gap between cells: 0.5 → 1.5
- Button system extracted to shared btn-* utility classes in app.css
- Replaced Google Calendar link + Google Maps with OSM
- Removed google icon from iconify subset

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/lib/calendar-ics.ts

@@ -122,25 +122,7 @@ export function downloadICS(item: CalendarItemICS, filename: string): void {
   URL.revokeObjectURL(url);
 }
 
-/** Google-Calendar's render-template URL. Times must be UTC, in
- *  YYYYMMDDTHHMMSSZ format, joined by `/`. */
-export function googleCalUrl(item: CalendarItemICS): string {
-  const start = item.start;
-  const end =
-    item.end ?? new Date(start.getTime() + 60 * 60 * 1000);
-  const dates = `${fmtICSDate(start)}/${fmtICSDate(end)}`;
-  const params = new URLSearchParams({
-    action: "TEMPLATE",
-    text: item.title,
-    dates,
-  });
-  if (item.description) params.set("details", item.description);
-  if (item.location) params.set("location", item.location);
-  return `https://calendar.google.com/calendar/render?${params.toString()}`;
-}
-
-/** Generic maps URL — Google Maps search by query. Safe with addresses
- *  or place names. */
+/** OpenStreetMap search URL for an address or place name. */
 export function mapsUrl(location: string): string {
-  return `https://www.google.com/maps/search/?api=1&query=${encodeURIComponent(location)}`;
+  return `https://www.openstreetmap.org/search?query=${encodeURIComponent(location)}`;
 }