Fix publish_release.sh to upload installer + AppImage; document host REQUIRE_SIGNIN_VIEW

- Script uploaded only the three portable binaries; v0.2.1 release was
  missing step-line-setup-0.2.1.exe and the AppImage. Now uploads the full
  set (extras when present), reuses existing releases (adds missing assets),
  and falls back to ~/.git-credentials basic auth when GITEA_TOKEN is unset
- Back-filled both missing assets onto the live v0.2.1 release via API
  (release now carries all 5 artifacts)
- TODO/RELEASING/MEMORY document the findings and the host admin steps for
  anonymous downloads ([service] REQUIRE_SIGNIN_VIEW)

docs/RELEASING.md

@@ -80,15 +80,22 @@ the NSIS installer requires `makensis` (covered by CI).
 
 The repository lives at `https://git.allucanget.biz/zwitschi/security-game`.
 
-Preferred path — use the helper script with a token:
+Preferred path — use the helper script. It needs either a token or the same
+credentials used by `git push` (it falls back to `~/.git-credentials`):
 
 ```bash
-GITEA_TOKEN=your_api_token ./tools/publish_release.sh 0.1.0
+GITEA_TOKEN=your_api_token ./tools/publish_release.sh 0.2.1
+# or simply: ./tools/publish_release.sh 0.2.1   (uses ~/.git-credentials)
 ```
 
-The script creates the release from `project.godot`'s `config/version`, uploads
-all three `build/` artifacts, and prints the release URL. The token needs only
-`write:repository` scope on the Gitea host.
+The script creates (or reuses) the release from `project.godot`'s
+`config/version`, uploads the three portable artifacts **plus** the NSIS
+installer and AppImage when present, and prints the release URL. If CI already
+published the release, re-running the script only adds missing assets.
+
+> **Host note**: the release is fully built by CI, but anonymous users can only
+> browse and download when the instance sets `[service] REQUIRE_SIGNIN_VIEW=false`
+> in `app.ini` (the repo itself is public). See the TODO for the exact steps.
 
 Manual alternative: