feat: add dynamic highlights carousel to Community homepage

[Bjjj834]

Stacked on #33. This PR's base is fix/armor-events-build so its diff shows only the feature. Merge #33 first; GitHub will retarget this PR to main when that branch is deleted. (Without #33, main does not build — pre-existing summerTeamPartyPath error.)

Summary

• Adds a Community Highlights carousel to the community homepage, directly below the hero and above the Impact Dashboard / section cards
• Surfaces the next upcoming event (live Google Calendar feed merged with the hardcoded events list), the latest news article (by real publication date from the News sheet), and the featured course
• Responsive, keyboard- and touch-accessible, honors prefers-reduced-motion, with independent loading/error/empty handling per data source

Product rationale

The homepage was entirely static — nothing on it changed between visits, so returning members had no reason to land there. This section makes the page reflect what is actually happening in the community right now: the event you can still register for, the newest AI news item, and a concrete course to start. Each slide has a meaningful CTA that routes into an existing flow (event page/registration, article, course), so the carousel is a discovery surface rather than a decoration.

Implementation

New files

• frontend/src/landing_page/landing_page_armor/communityHighlights.js — pure, unit-tested selectors (selectNextUpcomingEvent, selectLatestNews, selectFeaturedCourse, parseEventStart) plus fetch helpers with a module-level promise cache (no refetch on remount)
• frontend/src/landing_page/landing_page_armor/CommunityHighlightsCarousel.js — the carousel component (custom, no new dependencies)

Modified files (minimal extractions, no behavior change)

• ArmorEvents.js — export added to the existing GCAL_ID, GCAL_API_KEY, eventsData, parseCalendarEvent so the carousel imports the existing config instead of duplicating it
• ArmorNews.js — export added to DEFAULT_SHEET_ID, DEFAULT_NEWS_GID, tryCsvFallbacks, csvToMatrix, normalizeRows
• ArmorCourses.js — catalog exported; one course marked featured: true with a comment documenting the selection rule
• ArmorMain.js — renders <CommunityHighlightsCarousel /> between hero and <ImpactDashboard />

Behavior details

• Auto-advance every 7s; pauses on hover, while keyboard focus is inside, and when the tab is hidden; disabled entirely under prefers-reduced-motion (slide transition animation is also dropped)
• Prev/next buttons, pagination dots (aria-current), ArrowLeft/ArrowRight keys, touch swipe (40px threshold) — all without any third-party carousel library
• ARIA: aria-roledescription="carousel" region, role="group"/aria-roledescription="slide" slides, labeled controls; focus is never moved programmatically and never trapped
• Event slide: nearest future event; past events excluded; malformed/missing dates skipped (never guessed). Calendar-only events link to the Events page for registration instead of opening another modal on the homepage
• News slide: newest article by parsed publication date; undated articles are never promoted as "latest"
• Course slide: labeled "Featured Course" — the catalog has no publishedAt/createdAt/addedAt metadata, so no "New Course" claim is made; a test guards this
• Failure isolation: each source loads independently; a failed source only drops its slide; if nothing valid exists the section renders null (no empty shell)
• Analytics: homepage_highlight_view / homepage_highlight_next / homepage_highlight_previous / homepage_highlight_cta_click with slide_type (event/news/course) via the existing ReactGA4 setup

Screenshots

Verified at desktop (1440px), tablet (768px), and mobile (375px) viewports — screenshots captured locally during review (home-desktop.png, home-tablet.png, home-mobile.png; can be attached on request). Desktop shows image-left/content-right slides; mobile stacks media above text with tappable buttons and no horizontal overflow (scrollWidth === clientWidth verified at 375px).

Testing

Command	Result
npm run lint	✅ 0 errors (165 pre-existing warnings, unchanged from baseline; this PR adds none)
CI=true npx react-scripts test --watchAll=false	✅ 3 suites, 27/27 tests pass
npm run build	✅ compiles

New tests: communityHighlights.test.js (nearest-future selection, past/malformed dates excluded, same-day + in-progress events included, latest-news date logic, featured-course rule + metadata guard) and CommunityHighlightsCarousel.test.js (skeleton, navigation via buttons/keyboard, failed-source isolation, all-empty renders nothing, ARIA attributes, autoplay, reduced-motion, hover pause).

Manual verification against the running app: live calendar picked the nearest event (World Cup Party, Jul 19) over a later one; news slide matched the top item on the News page; keyboard arrows change slides; reduced-motion override showed no auto-advance after 9s and no animation class; remounting the homepage reused cached data (no duplicate calendar request); quiz and newsletter modals open and dismiss exactly as before.

Risks and limitations

• Data quality dependence: slides are only as good as the community calendar, News sheet, and course catalog. Hardcoded events without startISO rely on display-string date parsing (handled, with malformed dates skipped).
• Featured course is manual: selected via featured: true in ArmorCourses.js (documented in-code). If date metadata is added later, a guard test flags the opportunity to switch to a genuine "New Course".
• Pre-existing issues observed, out of scope: the Learning-Path quiz (4s) and Newsletter modal (30s/exit-intent) can stack on top of each other on first visit; ImpactDashboard refetches members/calendar on every homepage mount and embeds the shared Google API key (added in Upgrade Impact Dashboard with live stats and social share (closes #1) #32); classnames and react-icons are imported but not declared in package.json. None are touched by this PR.

Checklist

• Tests pass (27/27)
• Lint passes (0 errors)
• Build passes
• Keyboard navigation checked
• Mobile checked (375px, no horizontal overflow)
• Reduced motion checked (unit test + live matchMedia override)
• No secrets added, no existing key duplicated (exports + imports only)

🤖 Generated with Claude Code

[Bjjj834]

Note on CI: the CI workflow triggers only on pull requests targeting main, so no checks run while this PR is based on fix/armor-events-build. Once #33 merges (its CI is green ✅) and the branch is deleted, GitHub retargets this PR to main and CI will run automatically. Local verification on this branch: lint 0 errors, 27/27 tests, production build compiles.