chore: monorepo scaffold, CI, MIT license

Bun workspaces (server/web/shared), typecheck+test gates, Gitea CI.
Refs PAI-90.

tsconfig.base.json

@@ -0,0 +1,12 @@
+{
+  "compilerOptions": {
+    "strict": true,
+    "module": "ESNext",
+    "moduleResolution": "bundler",
+    "target": "ES2022",
+    "types": ["bun-types"],
+    "skipLibCheck": true,
+    "composite": true,
+    "verbatimModuleSyntax": true
+  }
+}