feat: add web search block functionality and integrate with existing plugins

- Introduced a new web search block plugin to handle web search queries and results.
- Updated copilot, doc block, and pro block plugins to include web search context in AI completions.
- Implemented utility functions for parsing and building web search markdown.
- Enhanced API to support web search requests and responses.
- Added configuration for web search URL and timeout settings.
- Updated size limit checks to account for web search content.

reports/searxng/searxng-engine-timings-final-20260609-132939.csv

@@ -0,0 +1,10 @@
+engine,shortcut,backend,categories,configured_timeout,bang_query,elapsed_ms,status_code,ok,result_count,result_engines,unresponsive_engines,errors
+360search,360so,360search,null,8.0,!360so OpenAI,572.9,200,True,5,"[""360search""]",[],
+crowdview,cv,json_engine,"""general""",,!cv OpenAI,970.4,200,True,40,"[""crowdview""]",[],
+yep,yep,yep,"""general""",,!yep OpenAI,1236.1,200,True,20,"[""yep""]",[],
+duckduckgo news,ddn,duckduckgo_extra,"[""news""]",,!ddn OpenAI,1251.7,200,True,30,"[""duckduckgo news""]",[],
+naver news,nvrn,naver,"[""news""]",,!nvrn OpenAI,1781.1,200,True,10,"[""naver news""]",[],
+searchmysite,sms,xpath,"""general""",,!sms OpenAI,2062.9,200,True,10,"[""searchmysite""]",[],
+mwmbl,mwm,mwmbl,null,,!mwm OpenAI,2474.9,200,True,34,"[""mwmbl""]",[],
+reuters,reu,reuters,null,,!reu OpenAI,3044.4,200,True,20,"[""reuters""]",[],
+startpage,sp,startpage,"[""general"", ""web""]",,!sp OpenAI,3639.6,200,True,10,"[""startpage""]",[],