feat: xAI image generate/edit, API key import, and per-provider timeouts

- Add dedicated xAI image adapter with generate + edit (multi-image) via
  /v1/images/generations and /v1/images/edits, plus aspect_ratio/resolution UI
- Support importing existing API keys and exposing connection api-key routes
- Add global/per-provider connect timeout overrides from settings
- Keep unrelated provider UX improvements on this branch; no Grok quota tracking

open-sse/handlers/imageGenerationCore.js

@@ -96,7 +96,7 @@ export async function handleImageGenerationCore({
   let requestBody;
 
   try {
-    url = adapter.buildUrl(model, credentials);
+    url = adapter.buildUrl(model, credentials, body);
     requestBody = await adapter.buildBody(model, body);
     headers = adapter.buildHeaders(credentials, requestBody, model, body);
   } catch (error) {
@@ -140,7 +140,7 @@ export async function handleImageGenerationCore({
       try {
         const retryBody = await adapter.buildBody(model, body);
         const retryHeaders = adapter.buildHeaders(credentials, retryBody, model, body);
-        const retryUrl = adapter.buildUrl(model, credentials);
+        const retryUrl = adapter.buildUrl(model, credentials, body);
         providerResponse = await fetch(retryUrl, {
           method: "POST",
           headers: retryHeaders,