Restructure repo so the light variant installs as theme 'tintenblau'

omarchy-theme-install clones the repo into ~/.config/omarchy/themes/<name>
and omarchy-theme-set stages only the repo root. Moving the light variant
to the root makes 'omarchy theme install' produce a working theme; the dark
variant stays as tintenblau-dark/ subfolder.

vscode.json

@@ -0,0 +1,4 @@
+{
+  "name": "Tintenblau",
+  "extension": "local.theme-tintenblau"
+}