M1: shared turn logic + characterization tests (39 green)

- npm workspaces: shared/, server/
- shared/turn.js: port turn logic verbatim from App.js (bugs preserved)
- 39 characterization tests lock current behavior
- gitignore: sqlite data, logs

package.json

@@ -2,6 +2,10 @@
   "name": "ttrpg-initiative-tracker",
   "version": "0.1.0",
   "private": true,
+  "workspaces": [
+    "server",
+    "shared"
+  ],
   "dependencies": {
     "@testing-library/jest-dom": "^5.17.0",
     "@testing-library/react": "^13.4.0",
@@ -20,7 +24,10 @@
     "start": "react-scripts start",
     "build": "react-scripts build",
     "test": "react-scripts test",
-    "eject": "react-scripts eject"
+    "eject": "react-scripts eject",
+    "server:dev": "npm run dev --workspace server",
+    "server:test": "npm test --workspace server",
+    "shared:test": "npm test --workspace shared"
   },
   "eslintConfig": {
     "extends": [