server : (webui) revamp the input area, plus many small UI improvements (#13365)

* rework the input area

* process selected file

* change all icons to heroicons

* fix thought process collapse

* move conversation more menu to sidebar

* sun icon --> moon icon

* rm default system message

* stricter upload file check, only allow image if server has mtmd

* build it

* add renaming

* better autoscroll

* build

* add conversation group

* fix scroll

* extra context first, then user input in the end

* fix <hr> tag

* clean up a bit

* build

* add mb-3 for <pre>

* throttle adjustTextareaHeight to make it less laggy

* (nits) missing padding in sidebar

* rm stray console log

tools/server/webui/src/Config.ts

@@ -12,7 +12,7 @@ export const CONFIG_DEFAULT = {
   // Note: in order not to introduce breaking changes, please keep the same data type (number, string, etc) if you want to change the default value. Do not use null or undefined for default value.
   // Do not use nested objects, keep it single level. Prefix the key if you need to group them.
   apiKey: '',
-  systemMessage: 'You are a helpful assistant.',
+  systemMessage: '',
   showTokensPerSecond: false,
   showThoughtInProgress: false,
   excludeThoughtOnReq: true,