a11y: make mobile menu toggle keyboard & screen-reader accessible

The mobile hamburger is a <div class="mobile-menu-icon"> with a click
handler, so it worked on tap but was invisible to keyboard and screen-reader
users. Expose it as a button in main.js: role="button", tabindex="0",
aria-label, aria-expanded toggling, and Enter/Space activation. Verified in
a headless browser (focusable, Enter opens, aria state flips).

Also adds docs/PRE-LAUNCH-CHECKLIST.md (dev-only, excluded from deploy):
inventory of remaining content placeholders for the public launch.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

docs/PRE-LAUNCH-CHECKLIST.md

@@ -0,0 +1,53 @@
+# MSOS Pre-Launch Placeholder Checklist
+
+_Auto-generated. Applies to EN + MK + SI unless noted. Tick as you replace._
+
+## 1. Homepage — template placeholder content (HIGH)
+- [ ] Replace **Lorem ipsum testimonials** on the homepage (en/mk/si `index.html`, testimonials section)
+- [ ] Replace the template line **"Everything you need to know about the product and billing"** with real MSOS copy
+
+## 2. "Coming soon" cards
+- [ ] Blog index: **9 'Coming soon' cards** — publish or hide (en/mk/si)
+- [ ] News index: **3 'Coming soon' cards** — publish or hide (en/mk/si)
+
+## 3. Student-guide hero images — 30 pages ×3 languages
+Each has a styled "Image placeholder" box awaiting a real hero image:
+- [ ] `student-welcome-guide/academic-life/`
+- [ ] `student-welcome-guide/administrative-basics/`
+- [ ] `student-welcome-guide/admission-and-enrolment/`
+- [ ] `student-welcome-guide/application-deadlines/`
+- [ ] `student-welcome-guide/arrival-checklist/`
+- [ ] `student-welcome-guide/bachelor-application/`
+- [ ] `student-welcome-guide/choose-a-programme/`
+- [ ] `student-welcome-guide/complete-student-journey/`
+- [ ] `student-welcome-guide/document-preparation/`
+- [ ] `student-welcome-guide/evs-application-guide/`
+- [ ] `student-welcome-guide/healthcare-in-slovenia/`
+- [ ] `student-welcome-guide/master-application/`
+- [ ] `student-welcome-guide/means-accommodation-address/`
+- [ ] `student-welcome-guide/official-sources-and-checklists/`
+- [ ] `student-welcome-guide/prepare-to-move/`
+- [ ] `student-welcome-guide/recognition-of-education/`
+- [ ] `student-welcome-guide/renew-change-graduate/`
+- [ ] `student-welcome-guide/rm-si-3-health-insurance/`
+- [ ] `student-welcome-guide/student-accommodation/`
+- [ ] `student-welcome-guide/student-budget/`
+- [ ] `student-welcome-guide/student-meals/`
+- [ ] `student-welcome-guide/student-organisations-and-extracurriculars/`
+- [ ] `student-welcome-guide/student-residence-permit/`
+- [ ] `student-welcome-guide/student-transport/`
+- [ ] `student-welcome-guide/student-work/`
+- [ ] `student-welcome-guide/study-cities/`
+- [ ] `student-welcome-guide/tuition-and-scholarships/`
+- [ ] `student-welcome-guide/visa-and-residence-explained/`
+- [ ] `student-welcome-guide/wellbeing-and-community/`
+- [ ] `student-welcome-guide/where-to-apply-for-residence/`
+
+## 4. MSOS Hub — temporary photos (see code comments)
+- [ ] `msos-hub/`: hub-story-bg (wide renovated-Hub shot)
+- [ ] `msos-hub/`: hub-use-img photos
+- [ ] `msos-hub/`: hub-shot gallery photos
+
+## 5. Verify (not placeholders, but confirm before launch)
+- [ ] Support page bank details real & correct (IBAN SI56 0284 3026 6115 703 / SWIFT LJBASI2X)
+- [ ] MK/SI meta descriptions on legal/msos-hub/support proofread by a native speaker