feat: Add DSS infrastructure, remove legacy admin-ui code

- Remove legacy admin-ui/js/ vanilla JS components
- Add .dss/ directory with core tokens, skins, themes
- Add Storybook configuration and generated stories
- Add DSS management scripts (dss-services, dss-init, dss-setup, dss-reset)
- Add MCP command definitions for DSS plugin
- Add Figma sync architecture and scripts
- Update pre-commit hooks with documentation validation
- Fix JSON trailing commas in skin files

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

.dss/themes/default.json

@@ -0,0 +1,18 @@
+{
+  "_meta": {
+    "name": "default",
+    "description": "Default theme - brand overrides on top of shadcn skin",
+    "version": "1.0.0",
+    "layer": "theme",
+    "extends": "skins/shadcn",
+    "contract_version": "1.0.0"
+  },
+  "color": {
+    "primary": { "value": "#18181b", "comment": "zinc-900 - brand primary" },
+    "primary-foreground": { "value": "#fafafa", "comment": "zinc-50" },
+    "ring": { "value": "#18181b", "comment": "matches primary" }
+  },
+  "radius": {
+    "lg": { "value": "0.5rem", "comment": "default border radius for cards" }
+  }
+}