Add photo copyright & usage clause (EN/MK/SI)

Add a "Photos, images & copyright" card to the Official information
(legal) page in all three languages, plus a short rights/removal note
on the Gallery and Events & Projects pages.

- Clarifies most images are MSOS property or used with permission, and
  that third-party images (Get to know Macedonia/Slovenia, Student
  Welcome Guide) remain their owners' property.
- Requires prior written permission to reuse MSOS's own images.
- Adds a photo-removal / consent-withdrawal path via info@msosorg.com.
- New shared .photo-rights-note style in css/pages/_gallery.css.

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

si/gallery/index.html

@@ -431,6 +431,7 @@
                     </div>
             </article>
         </section>
+        <p class="photo-rights-note">Fotografije v tej galeriji so last MSOS. Prosimo, da jih ne uporabljate brez našega pisnega dovoljenja. Za prošnjo za uporabo ali za odstranitev fotografije, na kateri ste, nam pišite na <a href="mailto:info@msosorg.com">info@msosorg.com</a>. Več na naši strani <a href="../../si/legal/">Uradni podatki</a>.</p>
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