refactor: cf-only deploy via dashboard, drop gh actions

- Default `npm run build` now produces a root-relative build (CF Pages
  custom domain at loto.miti99.com). The /loto basePath is opt-in via
  `npm run build:gh` for the rare manual GH Pages export.
- Removed both GitHub Actions deploy workflows (.github/workflows/) and
  the dangling `build:cf` script (it was identical to `build` after the
  default flip).
- next.config.mjs: simplified basePath logic — only `BUILD_PROFILE=gh`
  toggles a non-empty path; everything else (CF, local dev) is root.

.github/workflows/deploy-cloudflare-pages.yml

@@ -1,32 +0,0 @@
-name: Deploy to Cloudflare Pages
-
-on:
-  push:
-    branches: [master]
-  workflow_dispatch:
-
-permissions:
-  contents: read
-  deployments: write
-
-concurrency:
-  group: cf-pages
-  cancel-in-progress: true
-
-jobs:
-  deploy:
-    runs-on: ubuntu-latest
-    steps:
-      - uses: actions/checkout@v4
-      - uses: actions/setup-node@v4
-        with:
-          node-version: 20
-          cache: npm
-      - run: npm ci
-      - run: npm run build:cf
-      - name: Publish to Cloudflare Pages
-        uses: cloudflare/wrangler-action@v3
-        with:
-          apiToken: ${{ secrets.CLOUDFLARE_API_TOKEN }}
-          accountId: ${{ secrets.CLOUDFLARE_ACCOUNT_ID }}
-          command: pages deploy out --project-name=loto --branch=${{ github.ref_name }}

.github/workflows/deploy.yml

@@ -1,40 +0,0 @@
-name: Deploy to GitHub Pages
-
-on:
-  push:
-    branches: [master]
-  workflow_dispatch:
-
-permissions:
-  contents: read
-  pages: write
-  id-token: write
-
-concurrency:
-  group: pages
-  cancel-in-progress: true
-
-jobs:
-  build:
-    runs-on: ubuntu-latest
-    steps:
-      - uses: actions/checkout@v4
-      - uses: actions/setup-node@v4
-        with:
-          node-version: 20
-          cache: npm
-      - run: npm ci
-      - run: npm run build:gh
-      - uses: actions/upload-pages-artifact@v3
-        with:
-          path: out
-
-  deploy:
-    needs: build
-    runs-on: ubuntu-latest
-    environment:
-      name: github-pages
-      url: ${{ steps.deployment.outputs.page_url }}
-    steps:
-      - id: deployment
-        uses: actions/deploy-pages@v4