Fix case-insensitive auth and harden for production

- Fix login/register to treat usernames case-insensitively (HeagBoKaT == heagbokat) using LOWER() in SQL with JS .toLowerCase() for Unicode safety
- Add helmet for HTTP security headers and express-rate-limit on auth endpoints (20 req / 15 min) to prevent brute-force
- Lock CORS to ALLOWED_ORIGIN env var; warn if JWT_SECRET is the default dev key
- Serve built client/dist from Express so a single PM2 process handles everything
- Add deploy.sh, README.md with full first-run and auto-restart instructions, and server/.env.example

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

server/package-lock.json

@@ -10,6 +10,8 @@
         "cors": "^2.8.5",
         "dotenv": "^16.4.0",
         "express": "^4.21.0",
+        "express-rate-limit": "^8.5.2",
+        "helmet": "^8.2.0",
         "jsonwebtoken": "^9.0.2",
         "multer": "^1.4.5-lts.1",
         "sql.js": "^1.14.1"
@@ -18,6 +20,7 @@
         "@types/bcryptjs": "^2.4.6",
         "@types/cors": "^2.8.17",
         "@types/express": "^4.17.21",
+        "@types/express-rate-limit": "^5.1.3",
         "@types/jsonwebtoken": "^9.0.7",
         "@types/multer": "^1.4.12",
         "@types/node": "^22.0.0",
@@ -518,6 +521,16 @@
         "@types/serve-static": "^1"
       }
     },
+    "node_modules/@types/express-rate-limit": {
+      "version": "5.1.3",
+      "resolved": "https://registry.npmjs.org/@types/express-rate-limit/-/express-rate-limit-5.1.3.tgz",
+      "integrity": "sha512-H+TYy3K53uPU2TqPGFYaiWc2xJV6+bIFkDd/Ma2/h67Pa6ARk9kWE0p/K9OH1Okm0et9Sfm66fmXoAxsH2PHXg==",
+      "dev": true,
+      "license": "MIT",
+      "dependencies": {
+        "@types/express": "*"
+      }
+    },
     "node_modules/@types/express-serve-static-core": {
       "version": "4.19.8",
       "resolved": "https://registry.npmjs.org/@types/express-serve-static-core/-/express-serve-static-core-4.19.8.tgz",
@@ -1031,6 +1044,24 @@
         "url": "https://opencollective.com/express"
       }
     },
+    "node_modules/express-rate-limit": {
+      "version": "8.5.2",
+      "resolved": "https://registry.npmjs.org/express-rate-limit/-/express-rate-limit-8.5.2.tgz",
+      "integrity": "sha512-5Kb34ipNX694DH48vN9irak1Qx30nb0PLYHXfJgw4YEjiC3ZEmZJhwOp+VfiCYwFzvFTdB9QkArYS5kXa2cx2A==",
+      "license": "MIT",
+      "dependencies": {
+        "ip-address": "^10.2.0"
+      },
+      "engines": {
+        "node": ">= 16"
+      },
+      "funding": {
+        "url": "https://github.com/sponsors/express-rate-limit"
+      },
+      "peerDependencies": {
+        "express": ">= 4.11"
+      }
+    },
     "node_modules/finalhandler": {
       "version": "1.3.2",
       "resolved": "https://registry.npmjs.org/finalhandler/-/finalhandler-1.3.2.tgz",
@@ -1164,6 +1195,18 @@
         "node": ">= 0.4"
       }
     },
+    "node_modules/helmet": {
+      "version": "8.2.0",
+      "resolved": "https://registry.npmjs.org/helmet/-/helmet-8.2.0.tgz",
+      "integrity": "sha512-DRgTIUgnWcJ62KyarxxziuqYxKGnR6Rgg19BlbucN/dpmJbl1XOit6qvoOX0ZT+HhWe5OUVhU/a1zpGyc1xA0Q==",
+      "license": "MIT",
+      "engines": {
+        "node": ">=18.0.0"
+      },
+      "funding": {
+        "url": "https://github.com/sponsors/EvanHahn"
+      }
+    },
     "node_modules/http-errors": {
       "version": "2.0.1",
       "resolved": "https://registry.npmjs.org/http-errors/-/http-errors-2.0.1.tgz",
@@ -1202,6 +1245,15 @@
       "integrity": "sha512-k/vGaX4/Yla3WzyMCvTQOXYeIHvqOKtnqBduzTHpzpQZzAskKMhZ2K+EnBiSM9zGSoIFeMpXKxa4dYeZIQqewQ==",
       "license": "ISC"
     },
+    "node_modules/ip-address": {
+      "version": "10.2.0",
+      "resolved": "https://registry.npmjs.org/ip-address/-/ip-address-10.2.0.tgz",
+      "integrity": "sha512-/+S6j4E9AHvW9SWMSEY9Xfy66O5PWvVEJ08O0y5JGyEKQpojb0K0GKpz/v5HJ/G0vi3D2sjGK78119oXZeE0qA==",
+      "license": "MIT",
+      "engines": {
+        "node": ">= 12"
+      }
+    },
     "node_modules/ipaddr.js": {
       "version": "1.9.1",
       "resolved": "https://registry.npmjs.org/ipaddr.js/-/ipaddr.js-1.9.1.tgz",