merge trails function added (#627)

* merge trails function added

* fix conflict resolve issues

* avoid incorrect authorship when merging trail comments

* require edit access for all selected trails before merge

* fix likes checkbox binding in trail merge modal

* improve error handling

* require editable target and deletable sources for merge

* avoid duplicate trail fetch during merge

* prevent duplicate likes when merging trails

* check photo download responses during trail merge

* add merge completion toast notifications

* cleanup

* small fixes

* move merge code to backend, option to merge single trail selection with similar one, automatic merge for integrations add as option, maintenance page to find and merge similar trails added

* fix build error

* fix

* docu, beautifying, refactoring

---------

Co-authored-by: Flomp <Flomp@users.noreply.github.com>

docs/astro.config.mjs

@@ -55,6 +55,10 @@ export default defineConfig({
           label: 'Summit logs',
           link: '/use/summit-logs/'
         },
+        {
+          label: 'Merge trails',
+          link: '/use/merge-trails/'
+        },
         {
           label: 'Interact with the community',
           link: '/use/community-interaction/'
@@ -152,4 +156,4 @@ export default defineConfig({
     '/run/backup-server/': '/run/backend-configuration/backup-server/',
     '/run/custom-categories/': '/run/backend-configuration/custom-categories/',
   },
-});
+});