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/imageProviders/index.js

@@ -12,6 +12,7 @@ import blackForestLabs from "./blackForestLabs.js";
 import runwayml from "./runwayml.js";
 import cloudflareAi from "./cloudflareAi.js";
 import antigravity from "./antigravity.js";
+import xai from "./xai.js";
 
 const ADAPTERS = {
   openai: createOpenAIAdapter("openai"),
@@ -19,7 +20,7 @@ const ADAPTERS = {
   openrouter: createOpenAIAdapter("openrouter"),
   recraft: createOpenAIAdapter("recraft"),
   "vercel-ai-gateway": createOpenAIAdapter("vercel-ai-gateway"),
-  xai: createOpenAIAdapter("xai"),
+  xai,
   gemini,
   codex,
   sdwebui,