fix(api): use shared SOCKS5 flag reader in settings routes (#13646)

Both settings routes use the shared `isSocks5ProxyEnabled()` reader instead of a copied check (identical logic, no behavior change).

Maintainer rework before merge (kept the idea, no default behavior change):
- The source-grep tests were replaced by behavioral tests of both routes across the flag on/off matrix (`GET /api/settings/proxies` reports `socks5Enabled`; `PUT /api/settings/proxy` accepts socks5 or returns 400).

Validated first on the combined board of all 38 PRs of this batch (10 merged as-is, 28 after the maintainer rework) on top of release/v3.8.51 c0f92ec: typecheck:core, check:open-sse-typecheck and check:dashboard-typecheck clean; ESLint clean on every changed file; file-size (rebaselined for the combined growth), complexity, cognitive-complexity, changelog-integrity, docs-counts, docs-sync, migration-numbering and i18n new-key gates green; 735 focused node:test cases with the only batch-caused failure (a flag-count assertion) fixed. Then re-validated alone on the fresh release tip right before this merge: ESLint on the changed files, typecheck:core, check:open-sse-typecheck, the file-size/complexity/changelog gates and this PR's own tests.

Thanks @maxmad64bis!

src/app/api/settings/proxies/route.ts

@@ -1,3 +1,4 @@
+import { isSocks5ProxyEnabled } from "@omniroute/open-sse/utils/proxyDispatcher";
 import { listProxies } from "@/lib/db/proxies";
 import {
   handleProxyCreate,
@@ -42,10 +43,8 @@ export async function GET(request: Request) {
       // #5890: coarse relay health pulse for the dashboard — how many relay
       // probes have run, and how many came back alive.
       relayProbeStats: getRelayProbeStats(),
-      // Default ON (opt-out): only an explicit falsey value disables SOCKS5.
-      socks5Enabled: !["false", "0", "no", "off"].includes(
-        (process.env.ENABLE_SOCKS5_PROXY ?? "").trim().toLowerCase()
-      ),
+      // SOCKS5 defaults ON — see isSocks5ProxyEnabled().
+      socks5Enabled: isSocks5ProxyEnabled(),
     });
   } catch (error) {
     return createErrorResponseFromUnknown(error, "Failed to load proxies");

src/app/api/settings/proxy/route.ts

@@ -6,7 +6,10 @@ import {
   resolveProxyForConnection,
 } from "@/lib/db/settings";
 import { getProxyAssignments, getProxyById } from "@/lib/db/proxies";
-import { clearDispatcherCache } from "@omniroute/open-sse/utils/proxyDispatcher";
+import {
+  clearDispatcherCache,
+  isSocks5ProxyEnabled,
+} from "@omniroute/open-sse/utils/proxyDispatcher";
 import { updateProxyConfigSchema } from "@/shared/validation/schemas";
 import { isValidationFailure, validateBody } from "@/shared/validation/helpers";
 import {
@@ -29,21 +32,15 @@ const PROXY_LEVEL_TO_REGISTRY_SCOPE = {
   key: "account",
 } as const;
 
-function isSocks5Enabled() {
-  // Default ON (opt-out): only an explicit falsey value disables SOCKS5.
-  const raw = (process.env.ENABLE_SOCKS5_PROXY ?? "").trim().toLowerCase();
-  return !["false", "0", "no", "off"].includes(raw);
-}
-
 function getSupportedProxyTypes() {
-  if (isSocks5Enabled()) {
+  if (isSocks5ProxyEnabled()) {
     return new Set([...BASE_SUPPORTED_PROXY_TYPES, "socks5"]);
   }
   return BASE_SUPPORTED_PROXY_TYPES;
 }
 
 function supportedTypesMessage() {
-  return isSocks5Enabled() ? "http, https, or socks5" : "http or https";
+  return isSocks5ProxyEnabled() ? "http, https, or socks5" : "http or https";
 }
 
 function createInvalidProxyError(message: string): ApiRouteError {
@@ -104,7 +101,7 @@ function normalizeAndValidateProxy(
   }
 
   const type = String(proxy.type || "http").toLowerCase() as NonNullable<ProxyConfigInput["type"]>;
-  if (type === "socks5" && !isSocks5Enabled()) {
+  if (type === "socks5" && !isSocks5ProxyEnabled()) {
     throw createInvalidProxyError(
       "SOCKS5 proxy is disabled (remove ENABLE_SOCKS5_PROXY=false to enable — it is ON by default)"
     );