Migrate UI pages to Lit web components in antrea-ui-components

Replace the Clarity Core UI library with a new antrea-ui-components
package of Lit-based custom elements, and migrate all page-level React
components into it so a downstream Angular shell can consume them
without the React dependency.

New components library (client/web/antrea-ui-components):
- antrea-button, antrea-alert, antrea-card, antrea-input, antrea-nav:
  lightweight replacements for the Clarity Core primitives
- antrea-summary-page, antrea-settings-page: cluster info and feature
  gate management pages
- antrea-traceflow-page: DOT graph rendering via d3-graphviz, polling
  loop with retry-after support, live/dropped-only capture modes
- antrea-flow-visibility-page: SSE-backed live flow list with
  multi-select namespace/pod/service filtering, D3 force-simulation
  service map with namespace hulls, drag/zoom, and verdict-colored edges
- Shared lib: FlowStreamClient (SSE with reconnect), FlowStore (bounded
  LRU with sliding-window bit rate), typed API helpers, design tokens

React app (client/web/antrea-ui):
- Replace all page route files with thin Lit wrapper components that
  forward the auth token and bridge antrea-session-expired events to
  the Redux-backed logout flow
- Delete all React route files, page-level API modules, and store files
  that moved into the components library
- Move @types/d3 to regular dependencies so the Docker build
  (npm install --omit=dev) still installs the type declarations needed
  when antrea-ui compiles the components source directly

Author: heanlan

build/frontend.dockerfile

@@ -14,16 +14,25 @@
 
 FROM node:24-bullseye-slim as build-web
 
+# Optional: override the npm registry (e.g., for corporate proxies).
+# Leave unset to use the default registry (npmjs.org).
+ARG NPM_REGISTRY=""
+
+# Install antrea-ui-components dependencies first so the link: resolution can find 'lit'.
+WORKDIR /antrea-ui-components
+COPY client/web/antrea-ui-components/package.json client/web/antrea-ui-components/package-lock.json ./
+COPY client/web/antrea-ui-components/src ./src
+COPY client/web/antrea-ui-components/tsconfig.json ./
+RUN if [ -n "$NPM_REGISTRY" ]; then npm config set registry "$NPM_REGISTRY"; fi && \
+    npm install --omit=dev
+
 WORKDIR /app
 
 COPY client/web/antrea-ui/package.json .
 COPY client/web/antrea-ui/yarn.lock .
 COPY client/web/antrea-ui/.yarnrc.yml .
 COPY client/web/antrea-ui/.yarn ./.yarn
 
-# Optional: override the npm registry (e.g., for corporate proxies).
-# Leave unset to use the default registry (npmjs.org).
-ARG NPM_REGISTRY=""
 RUN if [ -n "$NPM_REGISTRY" ]; then \
       echo "npmRegistryServer: \"$NPM_REGISTRY\"" >> .yarnrc.yml; \
     fi

client/web/antrea-ui-components/.gitignore

@@ -0,0 +1,2 @@
+node_modules/
+dist/