feat: add sentinel dashboard roadmap and fix ci failures

- Create `docs/sentinel-dashboard-master-plan.md` and `docs/roadmap.md`.
- Fix Netlify `_headers` and `_redirects` formatting and synchronization issues.
- Refactor `backend/models/User.js` to eliminate code duplication (jscpd) and apply Standard JS style.
- Refactor `backend/server.js` to resolve Deno lint errors (no-undef, no-unused-vars, quotes, semi).
- Update `deno.json` to exclude `next-app` and other non-Deno directories.
- Incorporate code review feedback for documentation clarity and prerequisites.

Co-authored-by: OneFineStarstuff <87420139+OneFineStarstuff@users.noreply.github.com>

Author: google-labs-jules[bot]

_headers

@@ -1,6 +1,6 @@
 /*
-X-Frame-Options: DENY
-X-Content-Type-Options: nosniff
-Referrer-Policy: strict-origin-when-cross-origin
-Permissions-Policy: interest-cohort=()
-Strict-Transport-Security: max-age=31536000; includeSubDomains; preload
+  X-Frame-Options: DENY
+  X-Content-Type-Options: nosniff
+  Referrer-Policy: strict-origin-when-cross-origin
+  Permissions-Policy: interest-cohort=()
+  Strict-Transport-Security: max-age=31536000; includeSubDomains; preload

backend/models/User.js

@@ -6,11 +6,10 @@
 import { query } from '../config/database.js'
 
 function mapUser (user, includePassword = false) {
-  return {
+  const mapped = {
     id: user.id,
     username: user.username,
     email: user.email,
-    ...(includePassword && { password: user.password_hash }),
     encryptionSalt: user.encryption_salt,
     firstName: user.first_name,
     lastName: user.last_name,
@@ -24,6 +23,10 @@ function mapUser (user, includePassword = false) {
     avatarUrl: user.avatar_url,
     bio: user.bio
   }
+  if (includePassword) {
+    mapped.password = user.password_hash
+  }
+  return mapped
 }
 
 export async function createUser (userData) {