docs: publish docs/ to the GitHub wiki and reorganise the user guide

- scripts/publish-wiki.sh publishes every page listed in SECTIONS, copies
  images, writes a sectioned sidebar and footer, and removes stale pages.
  --check fails on links to missing files or headings and on docs pages
  that are neither published nor excluded.
- New wiki.yml runs the check on pull requests and pushes to main, and
  publishes when release.yml calls it or when started by hand.
- Split USER_GUIDE.md into topic pages (files, synced folders, photos,
  sharing, computers, launcher and tray); add Getting started and FAQ.
- Make the COPR repository the main Fedora path, with update and
  uninstall steps for every package type.
- Fix the stale CAPTCHA note in CLI.md, document pdfs unlock and lock,
  and drop the broken AGENTS.md link from CONTRIBUTING.md.

.github/ISSUE_TEMPLATE/config.yml

@@ -3,6 +3,9 @@ contact_links:
   - name: Security vulnerability
     url: https://github.com/narrrl/proton-drive-linux/security/advisories/new
     about: Report privately — never in a public issue.
+  - name: Troubleshooting and FAQ
+    url: https://github.com/narrrl/proton-drive-linux/wiki/Troubleshooting
+    about: Fixes for common problems, and what to include in a bug report.
   - name: Known issues
     url: https://github.com/narrrl/proton-drive-linux/blob/main/docs/BUGS.md
     about: The authoritative ledger of tracked bugs and their status.