feat(dashboard): add optional login authentication (#319)

Add session-based username/password auth for CCS dashboard:
- Backend: Express session middleware with bcrypt password verification
- Frontend: React AuthContext, login page, protected routes
- Config: dashboard_auth section in config.yaml + env var overrides
- Security: Rate limiting (5 attempts/15min), persistent session secret
- 16 unit tests for auth middleware

Auth disabled by default for backward compatibility.

package.json

@@ -81,11 +81,13 @@
     "postinstall": "node scripts/postinstall.js"
   },
   "dependencies": {
+    "bcrypt": "^6.0.0",
     "boxen": "^5.1.2",
     "chalk": "^4.1.2",
     "chokidar": "^3.6.0",
     "cli-table3": "^0.6.5",
     "express": "^4.18.2",
+    "express-session": "^1.18.2",
     "get-port": "^5.1.1",
     "gradient-string": "^2.0.2",
     "js-yaml": "^4.1.1",
@@ -104,8 +106,11 @@
     "@semantic-release/npm": "^13.1.3",
     "@semantic-release/release-notes-generator": "^14.1.0",
     "@tailwindcss/vite": "^4.1.17",
+    "@types/bcrypt": "^6.0.0",
     "@types/chokidar": "^2.1.7",
     "@types/express": "^4.17.21",
+    "@types/express-rate-limit": "6.0.0",
+    "@types/express-session": "^1.18.2",
     "@types/js-yaml": "^4.0.9",
     "@types/node": "^20.19.25",
     "@types/ws": "^8.5.10",