feat(web): comprehensive cleanup - rewrite Rules/ToS/Privacy, unify emails

- rewrite Rules, Terms of Service, Privacy Policy with original mxchat content
  (replace tchncs.de and riot.im fork artifacts)
- unify all support contacts to podpora@oscloud.cz
- list real bridges (6 only): WhatsApp, Telegram, Signal, Meta, Discord, Gmessages
  removing non-running ones (Google Chat, Instagram, Steam)
- remove OSCloud apps (miniflux/pairdrop/wallabag) - belong on docs.oscloud.cz
- fix broken footer in kontakty/index.html
- fix broken https://mxchat.cz/contact links
- update outdated mentions (riot.im, vector.im → Element)

index/kontakty/index.html

@@ -58,7 +58,7 @@ along with this program. If not, see <https://www.gnu.org/licenses/>.
           ><i class="fa fa-telegram"></i> Telegram</a>
         </nav>
       <nav>
-        <a href="mailto:podpora@mxchat.cz" class="btn" target="_blank">
+        <a href="mailto:podpora@oscloud.cz" class="btn" target="_blank">
     <i class="fa fa-envelope"></i> Email
   </a>
   <a href="https://keys.openpgp.org/vks/v1/by-fingerprint/33E90E50DCCD1604BCEA17EA28E9AF0110058235" class="btn" target="_blank">
@@ -70,7 +70,7 @@ along with this program. If not, see <https://www.gnu.org/licenses/>.
 
     <footer class="site-footer">
         <p>Copyright &copy; 2024-2026 Oscloud <a href="https://git.arch-linux.cz/Oscloud/web-mxchat" class="" target="_blank"
-          ><i class="fa fa-gitea"></i> Gitea</</p>
+          ><i class="fa fa-gitea"></i> Gitea</a></p>
     </footer>
   </body>
 </html>