Fix the repo icon path to avoid copying the file onto itself

fdroidserver's legacy index builder copies repo_icon into repo/icons/ by
its basename; pointing repo_icon at that destination made the copy a
same-file no-op that shutil.copyfile refuses, crashing every index
rebuild. The icon source now lives outside repo/icons/.

module.nix

@@ -34,11 +34,13 @@ let
     repo_name: ${cfg.repoName}
     repo_description: ${cfg.repoDescription}
     repo_keyalias: ${cfg.keyAlias}
-    # fdroidserver checks this path for existence relative to the cwd `fdroid
-    # update` runs in (stateDir), then copies it into repo/icons/ under its
-    # own basename — so this is deliberately already that destination path,
-    # which the sync script keeps populated before every run.
-    repo_icon: repo/icons/icon.png
+    # fdroidserver's legacy index builder checks this path for existence
+    # relative to the cwd `fdroid update` runs in (stateDir) and then
+    # `shutil.copyfile`s it into repo/icons/ under its own basename — which
+    # raises SameFileError if source and destination are the same path. So
+    # this has to name a *source* file outside repo/icons/, kept at
+    # ${cfg.stateDir}/icon.png by the sync script below.
+    repo_icon: icon.png
     keystore: ${cfg.keystoreFile}
     keystorepass: {env: FDROID_KEYSTORE_PASS}
     keypass: {env: FDROID_KEY_PASS}
@@ -76,7 +78,9 @@ let
     install -m 0600 ${repoConfig} ${cfg.stateDir}/config.yml
     # Kept populated every run rather than once, so an icon change here
     # propagates on the next sync without anyone having to touch the server.
-    install -D -m 0644 ${cfg.repoIcon} ${cfg.stateDir}/repo/icons/icon.png
+    # Lives next to repo/, not inside repo/icons/ itself — see repo_icon
+    # above for why that distinction matters.
+    install -m 0644 ${cfg.repoIcon} ${cfg.stateDir}/icon.png
     exec ${pythonEnv}/bin/python3 ${./fdroid-sync.py} ${syncConfig} "$@"
   '';