feat: add StroyBot app shell with URL routing

One web part replaces the separate stroy-bot-* web parts. The section and
its parameters live in the page query string (?page=objects&projectId=5),
so links can be copied, opened in a new tab and the browser Back button works.

- shared config: site/Dataverse/API addresses, list and table names
- HTTP layer behind IHttpClient so repositories can be unit-tested
- ui-kit AppLayout + Sidebar, placeholder for sections not ported yet
- migration checklist with every feature of the old web parts
- design tokens mirrored from ui-kit instead of 8 copies

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

package.json

@@ -15,6 +15,8 @@
     "@fluentui/react": "^8.106.4",
     "@microsoft/sp-component-base": "1.22.1",
     "@microsoft/sp-core-library": "1.22.1",
+    "@microsoft/sp-http": "1.22.1",
+    "@microsoft/sp-loader": "1.22.1",
     "@microsoft/sp-lodash-subset": "1.22.1",
     "@microsoft/sp-office-ui-fabric-core": "1.22.1",
     "@microsoft/sp-property-pane": "1.22.1",