feat(frontend)!: drop SetupWizardPage, backend URL via build-time VITE_*

Frontend no longer has any wizard flow. Backend URL is baked into the bundle
at build time via VITE_HF_BACKEND_BASE_URL (forwarded as a Dockerfile ARG
from compose).

- src/App.tsx: drop SetupWizardPage import + appState='setup' fallback +
  HF_WIZARD_PORT-via-localStorage probe. getApiBase() now reads
  import.meta.env.VITE_HF_BACKEND_BASE_URL with localStorage as an escape
  hatch for dev. When /config/status reports no admin yet, show a card
  prompting the operator to run `docker exec hf_backend hf-cli admin
  create-user ...`.
- src/pages/SetupWizardPage.tsx: deleted (~250 lines)
- src/index.css: drop .setup-wizard + .setup-* styles (~36 lines)
- src/vite-env.d.ts: add VITE_HF_BACKEND_BASE_URL to ImportMetaEnv
- Dockerfile: ARG VITE_HF_BACKEND_BASE_URL → ENV → npm run build

Build the prod image with:
  docker build --build-arg VITE_HF_BACKEND_BASE_URL=https://hf-api.hangman-lab.top \
    -t git.hangman-lab.top/zhi/harborforge-frontend:latest .

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Dockerfile

@@ -1,6 +1,14 @@
 # Build stage
 FROM node:20-alpine AS build
 WORKDIR /app
+
+# Build-time backend URL — Vite inlines this into the bundle. Passed as
+# `--build-arg VITE_HF_BACKEND_BASE_URL=https://hf-api.example.com` in
+# the compose file. Without it the bundle calls relative paths (only
+# works in dev with the Vite proxy).
+ARG VITE_HF_BACKEND_BASE_URL=""
+ENV VITE_HF_BACKEND_BASE_URL=${VITE_HF_BACKEND_BASE_URL}
+
 COPY package.json package-lock.json* ./
 RUN npm install
 COPY . .