Add Zod validation, fix mass assignment, remove test endpoints and dead code

- Add centralized Zod schemas (server/utils/schemas.js) and validateBody
  utility for all API endpoints
- Fix critical mass assignment in member creation: raw body no longer
  passed to new Member(), only validated fields (email, name, circle,
  contributionTier) are accepted
- Apply Zod validation to login, profile patch, event registration,
  updates, verify-payment, and admin event creation endpoints
- Fix logout cookie flags to match login (httpOnly: true, secure
  conditional on NODE_ENV)
- Delete unauthenticated test/debug endpoints (test-connection,
  test-subscription, test-bot)
- Remove sensitive console.log statements from Helcim and member
  endpoints
- Remove unused bcryptjs dependency
- Add 10MB file size limit on image uploads
- Use runtime config for JWT secret across all endpoints
- Add 38 validation tests (117 total, all passing)

package.json

@@ -19,8 +19,7 @@
     "@nuxt/ui": "^4.0.0",
     "@nuxtjs/plausible": "^3.0.1",
     "@slack/web-api": "^7.10.0",
-    "bcryptjs": "^3.0.2",
-    "chrono-node": "^2.8.4",
+"chrono-node": "^2.8.4",
     "cloudinary": "^2.7.0",
     "eslint": "^9.34.0",
     "isomorphic-dompurify": "^3.0.0",