feat(security,ci,ui): harden CI/CD, LuCI ACL, low-space updates and mobile layout

- ci: make frontend CI read-only with strict diff check and deterministic calls.json
- ci: pin external GitHub Actions in workflows to immutable commit SHAs
- ci: add openwrt-e2e blocking gate job running docker_e2e_test.sh
- fix(diagnostic): fix contstants.ts typo and update all 13 import sites
- fix(acl): remove unused /bin/busybox exec from rpcd ACL and add regression test
- feat(updates): add low-space update fallback when creating sing-box.old is impossible
- fix(routes): preserve dedicated Discord gateway subnets (162.159.128.0/21)
- feat(ui): implement responsive auto-fit grid and mobile modal viewport bounds
- test: add viewport regression test suite in vitest

luci-app-tachyon/root/usr/share/rpcd/acl.d/luci-app-tachyon.json

@@ -62,9 +62,6 @@
         ],
         "/usr/bin/nslookup": [
           "exec"
-        ],
-        "/bin/busybox": [
-          "exec"
         ]
       },
       "ubus": {