Add upcoming events page

[AJaccP]

As a visitor, I want a dedicated upcoming events page so I can quickly see what events are coming up next.

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🧠 Context

The nav already has a slot for events/upcoming but the page doesn't exist yet. The events section (layouts/_default/events.html) is a good reference for structure and CSS classes.

Since Hugo generates static HTML at build time, now reflects the build date — not the visitor's actual date. To handle this, Hugo renders all events upcoming as of the last build, and a small inline script removes any that have since passed using the browser's real current date. The script only runs on this page and does not affect /events.

If no cards remain after JS filtering, a fallback message with a link to /events is shown. Since Hugo can't know at build time whether all cards will be removed, this fallback is hidden by default and revealed by JS when needed.

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🛠️ Implementation Plan

1. Create content/events/upcoming/_index.md

   Similar to content/events/_index.md — set layout: upcoming-events and title: "Upcoming Events".

2. Create layouts/_default/upcoming-events.html

   Model the structure on layouts/_default/events.html. Use Hugo to filter events upcoming as of build time:

   {{ $today := time.AsTime (now.Format "2006-01-02") }}
   {{ $upcoming := (where (where .Site.RegularPages "Section" "events") ".Date" "ge" $today).ByDate }}

   Render each card with a data-date attribute on the wrapping <a>:

   <a data-date="{{ .Date.Format "2006-01-02" }}" class="event_card_link hvr-float" href="{{ .RelPermalink }}">

   Include a hidden fallback message (e.g. display: none) with a link to /events for when no cards remain.

3. Add an inline script that runs on page load:

   • Gets today's date from the browser
   • Removes any [data-date] cards whose date is before today
   • If no cards remain, reveals the fallback message

4. Verify with hugo server that:

   • Upcoming events display correctly
   • Manually setting the script's "today" to a future date hides all cards and reveals the fallback message

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✅ Acceptance Criteria

• /events/upcoming renders upcoming events sorted soonest-first
• Each event card has a data-date attribute
• Events that have passed since the last build are removed on page load
• When no upcoming events remain, the fallback message and link to /events are shown
• /events and other pages are unaffected
• Page style is consistent with the rest of the events section