Fix feedback spam: lock buttons after vote, add comment box on No

Voting now locks the widget for the page view (buttons disabled, chosen one highlighted, thank-you shown); reload to vote again. Fixes the CSS bug where display:flex overrode the hidden attribute so buttons stayed clickable. On No, an optional comment box posts to a separate Comment field. Adds a guarded [hidden] rule and selected/disabled/comment styles.

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

si/student-welcome-guide/arrival-checklist/index.html

@@ -277,6 +277,12 @@
                     </div>
                     <p class="guide-feedback-msg guide-feedback-yes" hidden>Hvala, veseli nas, da je bilo to koristno.</p>
                     <p class="guide-feedback-msg guide-feedback-no" hidden>Hvala za povratno informacijo. Pomagajte nam izboljšati stran in nam napišite, kaj je manjkalo, na <a href="mailto:info@msosorg.com?subject=Povratna%20informacija%20o%20vodniku%3A%20Kontrolni%20seznam%20ob%20prihodu">info@msosorg.com</a> ali vprašajte v naši <a href="https://invite.viber.com/?g2=AQA8mf%2BZki%2FEk1GS2lyGTD6tc7SdqKmI5pVkOKT1jVasvZz0Lhn8esKYxjza9xoy" target="_blank" rel="noopener">skupnosti na Viberju</a>.</p>
+                    <div class="guide-feedback-comment" hidden>
+                        <label class="guide-feedback-comment-label" for="fbc-arrival-checklist">Kaj je manjkalo ali bilo nejasno? (neobvezno)</label>
+                        <textarea id="fbc-arrival-checklist" class="guide-feedback-comment-input" rows="3" placeholder="Napišite, kaj lahko na tej strani izboljšamo"></textarea>
+                        <button type="button" class="guide-feedback-comment-send">Pošlji</button>
+                        <p class="guide-feedback-comment-thanks" hidden>Hvala, prejeli smo vaše sporočilo.</p>
+                    </div>
                 </div>
             </section>
         </article>