refactor(frontend): replace axios with the native Fetch API

Drop the axios (and qs) dependencies in favor of a native fetch wrapper.
axios only ever handled same-origin JSON/form calls, a CSRF header, a 401
redirect, and a 403-retry, all of which the platform now provides directly.

- New src/api/http-init.ts (replaces axios-init.ts) reimplements the
  request/response interceptors on fetch: base-path prefixing,
  X-Requested-With, same-origin credentials, the CSRF token on unsafe
  methods, a single 403 retry with token refresh, and the 401
  redirect-and-latch. A small encodeForm() reproduces qs's
  arrayFormat:'repeat' encoding, so the request wire format is unchanged.
- HttpUtil (src/utils/index.ts) keeps its public signatures and the Msg
  envelope, so the ~49 API call sites are untouched. HttpOptions is now
  hand-rolled instead of extending AxiosRequestConfig.
- PanelUpdateModal drops its lone direct axios.get in favor of HttpUtil.get
  with { silent, timeout }.
- Add tests for the fetch core (CSRF header, form/JSON/FormData bodies,
  base-path prefix, 403 retry, 401 redirect, tolerant body parse) and for
  HttpUtil's envelope unwrap / toast / error mapping; this logic was
  previously untested.
- Remove the vendor-axios manualChunks branch and the qs type shim, and
  reword stale "axios" mentions in docs and route comments.

frontend/package-lock.json

@@ -15,13 +15,11 @@
         "@tanstack/react-query": "^5.101.2",
         "@tanstack/react-query-devtools": "^5.101.2",
         "antd": "^6.5.0",
-        "axios": "^1.18.1",
         "codemirror": "^6.0.2",
         "dayjs": "^1.11.21",
         "i18next": "^26.3.4",
         "otpauth": "^9.5.1",
         "persian-calendar-suite": "^1.5.5",
-        "qs": "^6.15.3",
         "react": "^19.2.7",
         "react-dom": "^19.2.7",
         "react-i18next": "^17.0.8",
@@ -7060,6 +7058,7 @@
       "version": "1.13.4",
       "resolved": "https://registry.npmjs.org/object-inspect/-/object-inspect-1.13.4.tgz",
       "integrity": "sha512-W67iLl4J2EXEGTbfeHCffrjDfitvLANg0UlX3wFUUSTx92KXRFegMHUVgSqE+wvhAbi4WqjGg9czysTV2Epbew==",
+      "dev": true,
       "license": "MIT",
       "engines": {
         "node": ">= 0.4"
@@ -7474,22 +7473,6 @@
         "node": ">=6"
       }
     },
-    "node_modules/qs": {
-      "version": "6.15.3",
-      "resolved": "https://registry.npmjs.org/qs/-/qs-6.15.3.tgz",
-      "integrity": "sha512-O9gl3zCl5h5blw1KGUzQKhA5oUXSl8rwUIM5o0S3nCXMliSvy5Dzx7/DJcI+SwgICv+IneSZwhBh1oSyEHA71A==",
-      "license": "BSD-3-Clause",
-      "dependencies": {
-        "es-define-property": "^1.0.1",
-        "side-channel": "^1.1.1"
-      },
-      "engines": {
-        "node": ">=0.6"
-      },
-      "funding": {
-        "url": "https://github.com/sponsors/ljharb"
-      }
-    },
     "node_modules/querystringify": {
       "version": "2.2.0",
       "resolved": "https://registry.npmjs.org/querystringify/-/querystringify-2.2.0.tgz",
@@ -8190,6 +8173,7 @@
       "version": "1.1.1",
       "resolved": "https://registry.npmjs.org/side-channel/-/side-channel-1.1.1.tgz",
       "integrity": "sha512-6x6dK6zJdpTzF4sQeNYxwtvBzf6Eg4GtlesS94HOvTudUeyK2WXAaIfmDgsyslYrRBeFIlsi54AYsFGUuhmvrQ==",
+      "dev": true,
       "license": "MIT",
       "dependencies": {
         "es-errors": "^1.3.0",
@@ -8209,6 +8193,7 @@
       "version": "1.0.1",
       "resolved": "https://registry.npmjs.org/side-channel-list/-/side-channel-list-1.0.1.tgz",
       "integrity": "sha512-mjn/0bi/oUURjc5Xl7IaWi/OJJJumuoJFQJfDDyO46+hBWsfaVM65TBHq2eoZBhzl9EchxOijpkbRC8SVBQU0w==",
+      "dev": true,
       "license": "MIT",
       "dependencies": {
         "es-errors": "^1.3.0",
@@ -8225,6 +8210,7 @@
       "version": "1.0.1",
       "resolved": "https://registry.npmjs.org/side-channel-map/-/side-channel-map-1.0.1.tgz",
       "integrity": "sha512-VCjCNfgMsby3tTdo02nbjtM/ewra6jPHmpThenkTYh8pG9ucZ/1P8So4u4FGBek/BjpOVsDCMoLA/iuBKIFXRA==",
+      "dev": true,
       "license": "MIT",
       "dependencies": {
         "call-bound": "^1.0.2",
@@ -8243,6 +8229,7 @@
       "version": "1.0.2",
       "resolved": "https://registry.npmjs.org/side-channel-weakmap/-/side-channel-weakmap-1.0.2.tgz",
       "integrity": "sha512-WPS/HvHQTYnHisLo9McqBHOJk2FkHO/tlpvldyrnem4aeQp4hai3gythswg6p01oSoTl58rcpiFAjF2br2Ak2A==",
+      "dev": true,
       "license": "MIT",
       "dependencies": {
         "call-bound": "^1.0.2",