Fix Docker build: track web design tokens, anchor Design/ gitignore rule

The repo-root .gitignore rule `Design/` was unanchored, so with Git's
case-insensitive matching on Windows it also caught the Vue source dir
Web App/web/src/design/, leaving tokens.css untracked. Local builds worked
(file on disk) but the Git-derived Docker context failed on
`@import "./design/tokens.css"` (ENOENT).

Anchor the rule to /Design/ so it only excludes the top-level design-assets
folder, and commit the previously-ignored tokens.css source file.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

.gitignore

@@ -1,5 +1,9 @@
 # Design assets (excluded from version control)
-Design/
+# Anchored to the repo root so it only matches the top-level Design/ folder.
+# Unanchored `Design/` also matched nested source dirs like
+# Web App/web/src/design/ (Git is case-insensitive on Windows/macOS),
+# silently un-tracking real source files such as tokens.css.
+/Design/
 
 # Build artifacts
 *.exe