Fix all backend lint errors and security vulnerabilities

Backend lint (4 errors fixed):
- auth.ts: suppress @typescript-eslint/no-namespace on Express global
  augmentation (legitimate TS pattern for extending Request type)
- clients.ts: remove unnecessary \. escape in regex character class
- devices.ts: remove unnecessary \- escape by moving hyphen to front [-:]
- PollerService.ts: add comment to empty catch block

Security audit (high/critical CVEs fixed):
- frontend: bump axios (critical SSRF), lodash (high injection),
  follow-redirects (moderate) via npm audit fix
- backend: bump nodemailer 6.x → 8.0.5 (fixes 4 SMTP injection CVEs)

frontend/package-lock.json

@@ -2320,14 +2320,14 @@
       }
     },
     "node_modules/axios": {
-      "version": "1.13.6",
-      "resolved": "https://registry.npmjs.org/axios/-/axios-1.13.6.tgz",
-      "integrity": "sha512-ChTCHMouEe2kn713WHbQGcuYrr6fXTBiu460OTwWrWob16g1bXn4vtz07Ope7ewMozJAnEquLk5lWQWtBig9DQ==",
+      "version": "1.15.0",
+      "resolved": "https://registry.npmjs.org/axios/-/axios-1.15.0.tgz",
+      "integrity": "sha512-wWyJDlAatxk30ZJer+GeCWS209sA42X+N5jU2jy6oHTp7ufw8uzUTVFBX9+wTfAlhiJXGS0Bq7X6efruWjuK9Q==",
       "license": "MIT",
       "dependencies": {
         "follow-redirects": "^1.15.11",
         "form-data": "^4.0.5",
-        "proxy-from-env": "^1.1.0"
+        "proxy-from-env": "^2.1.0"
       }
     },
     "node_modules/balanced-match": {
@@ -3700,9 +3700,9 @@
       "license": "ISC"
     },
     "node_modules/follow-redirects": {
-      "version": "1.15.11",
-      "resolved": "https://registry.npmjs.org/follow-redirects/-/follow-redirects-1.15.11.tgz",
-      "integrity": "sha512-deG2P0JfjrTxl50XGCDyfI97ZGVCxIpfKYmfyrQ54n5FO/0gfIES8C/Psl6kWVDolizcaaxZJnTS0QSMxvnsBQ==",
+      "version": "1.16.0",
+      "resolved": "https://registry.npmjs.org/follow-redirects/-/follow-redirects-1.16.0.tgz",
+      "integrity": "sha512-y5rN/uOsadFT/JfYwhxRS5R7Qce+g3zG97+JrtFZlC9klX/W5hD7iiLzScI4nZqUS7DNUdhPgw4xI8W2LuXlUw==",
       "funding": [
         {
           "type": "individual",
@@ -4715,9 +4715,9 @@
       }
     },
     "node_modules/lodash": {
-      "version": "4.17.23",
-      "resolved": "https://registry.npmjs.org/lodash/-/lodash-4.17.23.tgz",
-      "integrity": "sha512-LgVTMpQtIopCi79SJeDiP0TfWi5CNEc/L/aRdTh3yIvmZXTnheWpKjSZhnvMl8iXbC1tFg9gdHHDMLoV7CnG+w==",
+      "version": "4.18.1",
+      "resolved": "https://registry.npmjs.org/lodash/-/lodash-4.18.1.tgz",
+      "integrity": "sha512-dMInicTPVE8d1e5otfwmmjlxkZoUpiVLwyeTdUsi/Caj/gfzzblBcCE5sRHV/AsjuCmxWrte2TNGSYuCeCq+0Q==",
       "license": "MIT"
     },
     "node_modules/lodash.merge": {
@@ -5371,10 +5371,13 @@
       "license": "MIT"
     },
     "node_modules/proxy-from-env": {
-      "version": "1.1.0",
-      "resolved": "https://registry.npmjs.org/proxy-from-env/-/proxy-from-env-1.1.0.tgz",
-      "integrity": "sha512-D+zkORCbA9f1tdWRK0RaCR3GPv50cMxcrz4X8k5LTSUD1Dkw47mKJEZQNunItRTkWwgtaUSo1RVFRIG9ZXiFYg==",
-      "license": "MIT"
+      "version": "2.1.0",
+      "resolved": "https://registry.npmjs.org/proxy-from-env/-/proxy-from-env-2.1.0.tgz",
+      "integrity": "sha512-cJ+oHTW1VAEa8cJslgmUZrc+sjRKgAKl3Zyse6+PV38hZe/V6Z14TbCuXcan9F9ghlz4QrFr2c92TNF82UkYHA==",
+      "license": "MIT",
+      "engines": {
+        "node": ">=10"
+      }
     },
     "node_modules/punycode": {
       "version": "2.3.1",