refactor(fastfetch): merge the mac and kde configs into common

One Fastfetch package now serves both platforms. The logo is sent
inline through the kitty graphics protocol from a pre-encoded
albedo.kitty, which works in Ghostty and Kwi alike, so the separate
kitty-direct (mac) and Konsole (kde) variants are no longer needed.

common/fastfetch/README.md

@@ -0,0 +1,17 @@
+# Fastfetch
+
+```sh
+stow -d common -t "$HOME" fastfetch
+```
+
+The logo is `albedo.png`, sent inline through the kitty graphics protocol from
+the pre-encoded `albedo.kitty`. This works in Ghostty and Kwi. The
+`kitty-direct` logo type is not used because Kwi ignores images passed as a
+file path.
+
+After changing `albedo.png` or the logo size in `config.jsonc`, regenerate the
+logo from the repository root:
+
+```sh
+python3 common/fastfetch/build.py
+```