Revamp repo header (#27760)

Redesign repo header with following new aspects:
- responsive & better-looking repo title
- hide repo button text instead of icons in mobile view
- use same tab style as on explore and org page

<details>
<summary>Before:</summary>


![grafik](57360b77-d43c-49ac-b798-2363c03da7ec)

![grafik](d4117f79-a5f5-4f36-bf65-bbada3e7e73b)

![grafik](e26f967f-e264-4337-9925-3d942e04fd6d)

![grafik](b4683c8d-9c6a-4089-afa7-8dd219e43a46)


</details>

<details>
<summary>After:</summary>


![grafik](8ddbc9f6-53c7-4e4e-bea9-704fd93524ca)

![grafik](c0588aa9-788d-469c-98a0-81484fbd220c)

![grafik](206e931e-404d-4d1b-92ce-908698addfcc)

![grafik](a508f9c8-fadc-4a85-94ba-18796f77e07b)

web_src/css/index.css

@@ -47,6 +47,7 @@
 @import "./repo/list-header.css";
 @import "./repo/linebutton.css";
 @import "./repo/wiki.css";
+@import "./repo/header.css";
 
 @import "./editor/fileeditor.css";
 @import "./editor/combomarkdowneditor.css";