Add ESLint + Prettier + EditorConfig tooling at repo root

v1.0 Phase 1.1 — repo-wide lint/format baseline.

- eslint.config.mjs (flat config) lints server, client, shared
- .prettierrc.json, .prettierignore, .editorconfig, .nvmrc
- Root package.json holds shared devDeps; per-package scripts keep
  their typecheck + test runners
- Fix 7 lint issues surfaced by the baseline run:
  - TicketDetail.tsx: replace ternary-with-side-effects with if/else
  - admin/Users.tsx: escape apostrophe in JSX
  - errorHandler.ts: typed err as unknown with ErrorLike refinement
  - users.ts: Prisma.UserUpdateInput instead of Record<string, any>
  - seed.ts: drop unused goddard binding
- Run prettier across tracked sources for a clean formatting baseline

package.json

@@ -0,0 +1,23 @@
+{
+  "name": "ticketing-system",
+  "private": true,
+  "version": "1.0.0",
+  "description": "Internal ticketing system — monorepo root (tooling only)",
+  "scripts": {
+    "lint": "eslint .",
+    "lint:fix": "eslint . --fix",
+    "format": "prettier --write .",
+    "format:check": "prettier --check .",
+    "typecheck": "npm run typecheck --prefix server && npm run typecheck --prefix client",
+    "test": "npm test --prefix server && npm test --prefix client"
+  },
+  "devDependencies": {
+    "@eslint/js": "^9.17.0",
+    "eslint": "^9.17.0",
+    "eslint-plugin-react": "^7.37.3",
+    "eslint-plugin-react-hooks": "^5.1.0",
+    "globals": "^15.14.0",
+    "prettier": "^3.4.2",
+    "typescript-eslint": "^8.18.2"
+  }
+}