[KYUUBI #7386] Remove axios dependency and replace with native fetch in web-ui

### Why are the changes needed?

Replace axios with the native Fetch API in request.ts, removing the axios dependency from package.json. Reducing the dependent libraries to reduce the possibility of supply chain attack and to reduce future maintenance cost. Enforce Node.js >=18 via the engines field and update README accordingly.

### How was this patch tested?

Covered by the existing unit tests.

### Was this patch authored or co-authored using generative AI tooling?

Generated-by: Claude Code (Claude Opus 4.6)

Closes #7386 from aajisaka/remove-axios.

Closes #7386

75c0402 [Cheng Pan] fix lint
11dc81e [Cheng Pan] Fix login failure and preserve server error messages
6cfb0b3 [Akira Ajisaka] Address review comments
c0634b7 [Akira Ajisaka] Remove axios dependency and replace with native fetch in web-ui

Lead-authored-by: Akira Ajisaka <aajisaka@apache.org>
Co-authored-by: Cheng Pan <chengpan@apache.org>
Signed-off-by: Cheng Pan <chengpan@apache.org>

Author: aajisaka

LICENSE-binary

@@ -442,12 +442,6 @@ is auto-generated by `pnpm licenses list --prod`.
 ├────────────────────────────────────┼──────────────┤
 │ async-validator                    │ MIT          │
 ├────────────────────────────────────┼──────────────┤
-│ asynckit                           │ MIT          │
-├────────────────────────────────────┼──────────────┤
-│ axios                              │ MIT          │
-├────────────────────────────────────┼──────────────┤
-│ combined-stream                    │ MIT          │
-├────────────────────────────────────┼──────────────┤
 │ commander                          │ MIT          │
 ├────────────────────────────────────┼──────────────┤
 │ csstype                            │ MIT          │
@@ -456,8 +450,6 @@ is auto-generated by `pnpm licenses list --prod`.
 ├────────────────────────────────────┼──────────────┤
 │ dayjs                              │ MIT          │
 ├────────────────────────────────────┼──────────────┤
-│ delayed-stream                     │ MIT          │
-├────────────────────────────────────┼──────────────┤
 │ discontinuous-range                │ MIT          │
 ├────────────────────────────────────┼──────────────┤
 │ element-plus                       │ MIT          │
@@ -466,10 +458,6 @@ is auto-generated by `pnpm licenses list --prod`.
 ├────────────────────────────────────┼──────────────┤
 │ estree-walker                      │ MIT          │
 ├────────────────────────────────────┼──────────────┤
-│ follow-redirects                   │ MIT          │
-├────────────────────────────────────┼──────────────┤
-│ form-data                          │ MIT          │
-├────────────────────────────────────┼──────────────┤
 │ get-stdin                          │ MIT          │
 ├────────────────────────────────────┼──────────────┤
 │ lodash                             │ MIT          │
@@ -482,10 +470,6 @@ is auto-generated by `pnpm licenses list --prod`.
 ├────────────────────────────────────┼──────────────┤
 │ memoize-one                        │ MIT          │
 ├────────────────────────────────────┼──────────────┤
-│ mime-db                            │ MIT          │
-├────────────────────────────────────┼──────────────┤
-│ mime-types                         │ MIT          │
-├────────────────────────────────────┼──────────────┤
 │ monaco-editor                      │ MIT          │
 ├────────────────────────────────────┼──────────────┤
 │ nanoid                             │ MIT          │
@@ -498,8 +482,6 @@ is auto-generated by `pnpm licenses list --prod`.
 ├────────────────────────────────────┼──────────────┤
 │ postcss                            │ MIT          │
 ├────────────────────────────────────┼──────────────┤
-│ proxy-from-env                     │ MIT          │
-├────────────────────────────────────┼──────────────┤
 │ randexp                            │ MIT          │
 ├────────────────────────────────────┼──────────────┤
 │ ret                                │ MIT          │

kyuubi-server/web-ui/README.md

@@ -2,7 +2,7 @@
 
 ### Start Using
 
-For the best experience, we recommend using `node 16.x.x`.
+Node.js 18 or higher is required.
 You can learn how to install the corresponding version from its official website.
 
 - [node](https://nodejs.org/en/)