feat: add COHERE_BASE_URL configuration support for custom Cohere rerank endpoints

- Add cohereBaseUrl to webSearchSchema configuration
- Update loadWebSearchConfig to load cohereBaseUrl from environment
- Add cohereBaseUrl to TWebSearchKeys type definition
- Configure cohereBaseUrl as optional parameter for cohere reranker
- Add COHERE_BASE_URL documentation to .env.example

This enables configuration of custom Cohere endpoints (such as LiteLLM proxy)
for web search reranking. The configuration infrastructure is ready for when
the @librechat/agents package supports custom base URLs.

Usage:
COHERE_BASE_URL=http://litellm:8000/v1
COHERE_API_KEY=your_api_key

.env.example

@@ -814,6 +814,7 @@ OPENWEATHER_API_KEY=
 # JINA_API_KEY=your_jina_api_key
 # or
 # COHERE_API_KEY=your_cohere_api_key
+# COHERE_BASE_URL=your_custom_cohere_base_url
 
 #======================#
 # MCP Configuration    #

packages/data-provider/src/config.ts

@@ -836,6 +836,7 @@ export const webSearchSchema = z.object({
   jinaApiKey: z.string().optional().default('${JINA_API_KEY}'),
   jinaApiUrl: z.string().optional().default('${JINA_API_URL}'),
   cohereApiKey: z.string().optional().default('${COHERE_API_KEY}'),
+  cohereBaseUrl: z.string().optional().default('${COHERE_BASE_URL}'),
   searchProvider: z.nativeEnum(SearchProviders).optional(),
   scraperProvider: z.nativeEnum(ScraperProviders).optional(),
   rerankerType: z.nativeEnum(RerankerTypes).optional(),

packages/data-schemas/src/app/web.ts

@@ -30,7 +30,11 @@ export const webSearchAuth = {
       /** Optional (0) */
       jinaApiUrl: 0 as const,
     },
-    cohere: { cohereApiKey: 1 as const },
+    cohere: {
+      cohereApiKey: 1 as const,
+      /** Optional (0) */
+      cohereBaseUrl: 0 as const,
+    },
   },
 };
 
@@ -72,6 +76,7 @@ export function loadWebSearchConfig(
   const jinaApiKey = config?.jinaApiKey ?? '${JINA_API_KEY}';
   const jinaApiUrl = config?.jinaApiUrl ?? '${JINA_API_URL}';
   const cohereApiKey = config?.cohereApiKey ?? '${COHERE_API_KEY}';
+  const cohereBaseUrl = config?.cohereBaseUrl ?? '${COHERE_BASE_URL}';
   const safeSearch = config?.safeSearch ?? SafeSearchTypes.MODERATE;
 
   return {
@@ -80,6 +85,7 @@ export function loadWebSearchConfig(
     jinaApiKey,
     jinaApiUrl,
     cohereApiKey,
+    cohereBaseUrl,
     serperApiKey,
     searxngApiKey,
     firecrawlApiKey,

packages/data-schemas/src/types/web.ts

@@ -9,7 +9,8 @@ export type TWebSearchKeys =
   | 'firecrawlVersion'
   | 'jinaApiKey'
   | 'jinaApiUrl'
-  | 'cohereApiKey';
+  | 'cohereApiKey'
+  | 'cohereBaseUrl';
 
 export type TWebSearchCategories =
   | SearchCategories.PROVIDERS