Fix: Add missing glm-cn provider definition for Web UI discovery (#186)

- Add glm-cn to APIKEY_PROVIDERS in src/shared/constants/providers.js
- Align with existing glm-cn model definitions in providerModels.js
- Users can now see and select GLM (China) option in Web UI
- Follows same pattern as minimax-cn (red color for China region)

src/shared/constants/providers.js

@@ -23,6 +23,7 @@ export const OAUTH_PROVIDERS = {
 export const APIKEY_PROVIDERS = {
   openrouter: { id: "openrouter", alias: "openrouter", name: "OpenRouter", icon: "router", color: "#F97316", textIcon: "OR", passthroughModels: true, website: "https://openrouter.ai" },
   glm: { id: "glm", alias: "glm", name: "GLM Coding", icon: "code", color: "#2563EB", textIcon: "GL", website: "https://open.bigmodel.cn" },
+  "glm-cn": { id: "glm-cn", alias: "glm-cn", name: "GLM (China)", icon: "code", color: "#DC2626", textIcon: "GC", website: "https://open.bigmodel.cn" },
   kimi: { id: "kimi", alias: "kimi", name: "Kimi", icon: "psychology", color: "#1E3A8A", textIcon: "KM", website: "https://kimi.moonshot.cn" },
   minimax: { id: "minimax", alias: "minimax", name: "Minimax Coding", icon: "memory", color: "#7C3AED", textIcon: "MM", website: "https://www.minimaxi.com" },
   "minimax-cn": { id: "minimax-cn", alias: "minimax-cn", name: "Minimax (China)", icon: "memory", color: "#DC2626", textIcon: "MC", website: "https://www.minimaxi.com" },