Refresh screenshot galleries and repair portal upgrades

Use the September 30 hero on the website and README, add a shared screenshot gallery, and remove the old showcase images. Build image links locally and clean generated site output.

Back up the known development portal override during installation and report custom overrides before building. Keep source selections clear while letting blur show through unselected rows.

README.md

@@ -7,6 +7,7 @@
 <p align="center">
   <a href="docs/installation.md">Install</a> ·
   <a href="docs/configuration.md">Configure</a> ·
+  <a href="docs/screenshots.md">Screenshots</a> ·
   <a href="docs/README.md">Documentation</a>
 </p>
 
@@ -14,7 +15,9 @@ Ferese is a Linux desktop with scrolling columns, tree tiling, and floating
 windows. It includes a top bar, Settings, notifications, desktop widgets, a
 lock screen, and screen sharing. Change themes and settings without restarting.
 
-![Ferese Blue desktop with Settings, Control Center, and a clock widget](docs/images/ferese-desktop.webp)
+![Ferese Blue desktop with Settings and Control Center](docs/images/screenshots/ferese-main-hero.png)
+
+[View all screenshots](docs/screenshots.md).
 
 ## Features
 
@@ -25,7 +28,6 @@ lock screen, and screen sharing. Change themes and settings without restarting.
 - Clock and sticky-note widgets.
 - Screenshots with Satty editing, screen sharing, and top-bar recording.
 
-![Ferese Overview showing windows and workspaces](docs/images/ferese-overview.webp)
 
 ## Install
 
@@ -47,8 +49,6 @@ See [Installation](docs/installation.md) for previews, updates, and recovery.
 Open **Control Center → Settings**, or edit `~/.config/ferese/config.kdl`.
 Changes reload automatically; invalid edits keep the last working configuration.
 
-![Ferese Settings and Control Center in Gruvbox](docs/images/ferese-gruvbox.webp)
-
 See the [configuration reference](docs/configuration.md) and
 [example config](packaging/config.kdl).