feat(openwebui): add web search config and pipelines secret

- Introduce `PIPELINES_API_KEY` in the secrets file to secure pipelines communication
- Replace hardcoded RAG and web search URLs with template variables, enabling flexible configuration
- Add new template variables (`ENABLE_WEB_SEARCH`, `WEB_SEARCH_ENGINE`, `WEB_LOADER_ENGINE`, `SEARXNG_QUERY_URL`, `EXTERNAL_WEB_LOADER_URL`) with defaults
- Include OpenWebUI secret env file in the service definition for consistent secret injection
- Set `ENABLE_PERSISTENT_CONFIG` to false to align with the parametrized deployment approach

These changes decouple service endpoints from the deployment template, allowing users to easily customize web search and RAG integrations without modifying service definitions.

openwebui/template.json

@@ -103,6 +103,41 @@
             "value": "",
             "required": "true",
             "generated": "random|sha256|20"
-        }
+        },
+        {
+            "description": "Enable web search",
+            "key": "ENABLE_WEB_SEARCH",
+            "value": "true",
+            "info": "Optional web search enabling, keep it empty if you don't want it",
+            "advanced": "true"
+        },
+        {
+            "description": "Web search engine",
+            "key": "WEB_SEARCH_ENGINE",
+            "value": "searxng",
+            "info": "Optional web search engine Searxng, keep it empty if you don't want it or define any other if you have",
+            "advanced": "true"
+        },
+        {
+            "description": "External web search engine",
+            "key": "WEB_LOADER_ENGINE",
+            "value": "external",
+            "info": "If optional web search engine defined, keep it as is, otherwise keep it empty",
+            "advanced": "true"
+        },
+        {
+            "description": "Web",
+            "key": "SEARXNG_QUERY_URL",
+            "value": "http://openwebuisearxng-app:8080/search?q=<query>",
+            "info": "Optional web search engine Searxng, keep it empty if you don't want it",
+            "advanced": "true"
+        },
+        {
+            "description": "External web search engine",
+            "key": "EXTERNAL_WEB_LOADER_URL",
+            "value": "http://openwebuicrawl4ai-app:11235",
+            "info": "Optional crawl4ai application url, keep it as is, otherwise keep it empty",
+            "advanced": "true"
+        }    
     ]
 }