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.

docs/PHOTOS.md

@@ -0,0 +1,77 @@
+# Photos
+
+The **Photos** page of the app shows your Proton Photos library. Photos are stored apart from
+My files, so they do not appear in `~/ProtonDrive`.
+
+- [Timeline](#timeline)
+- [Albums](#albums)
+- [Places](#places)
+- [Viewer and duplicates](#viewer-and-duplicates)
+- [Importing from Google Photos](#importing-from-google-photos)
+- [Fixing photos filed under the wrong date](#fixing-photos-filed-under-the-wrong-date)
+
+![The Photos timeline](../images/photos.png)
+
+## Timeline
+
+- The timeline groups photos by day, month or year as you zoom. Drag the scrubber on the right
+  edge to jump through the years.
+- **On this day** shows photos taken on the same date in earlier years.
+- **Filters** narrow the timeline to images, videos or RAW files, to favorites, or to photos that
+  are in no album.
+- **RAW + JPEG pairs** of the same shot show as one tile. The viewer switches between the two, and
+  moving the tile to the Trash removes both.
+- **Upload** adds photos from this computer.
+
+## Albums
+
+**Albums** lists your own albums and the albums others share with you. Create, rename and delete
+albums, and add or remove photos. Deleting an album keeps its photos in the timeline.
+
+## Places
+
+![Places on the map](../images/photos_map.png)
+
+**Places** groups photos by the town they were taken in, as cards or on a map. Town names come
+from [GeoNames](https://www.geonames.org/) data (CC BY 4.0) and the map from
+[Natural Earth](https://www.naturalearthdata.com/) (public domain). Both ship with the app, so
+nothing is fetched online.
+
+A street map from [OpenFreeMap](https://openfreemap.org/) (© OpenStreetMap contributors) can be
+turned on under **Preferences → General → Appearance**. It is off by default, because the map
+server learns which areas you look at.
+
+## Viewer and duplicates
+
+- The viewer marks favorites, shows EXIF details, shows a photo on the map, and runs a slideshow
+  (F5).
+- **Find Duplicates…** in the page menu lists byte-identical copies. Turn on **Similar** to also
+  find resized or re-encoded copies and burst shots.
+
+## Importing from Google Photos
+
+1. Request a [Google Takeout](https://takeout.google.com/) export of Google Photos and download
+   every `.zip` of it.
+2. In the app, open the **Upload** menu on the Photos page and choose **Import from Google
+   Photos…**. Select all the `.zip` files at once, because a photo and its details are often in
+   different parts of the export.
+
+From a terminal:
+
+```bash
+pdfs import-google-photos --dry-run ~/Downloads/takeout-*.zip   # show what would happen
+pdfs import-google-photos --wait ~/Downloads/takeout-*.zip
+```
+
+The import recreates your albums and takes capture dates and locations from the export. Photos
+already in your library are skipped, so an interrupted import can simply be run again.
+`pdfs import-status` shows how far an import is, and `pdfs cancel-import` stops it.
+
+## Fixing photos filed under the wrong date
+
+Photos from an earlier import sometimes sit under the day they were uploaded instead of the day
+they were taken. `pdfs redate-photos --dry-run` finds those whose file name carries a different
+date, and `pdfs redate-photos` fixes them.
+
+Proton cannot change a capture date in place. So each fix uploads the photo again with the right
+date and moves the original to the Trash. Favorites and albums are kept.