chore: migrate to Nix flakes, remove Docker and legacy configs

Remove all Docker files, Vercel config, Verdaccio, and old CI workflow.
Standardize on nodejs_22 across devShell and nix build helpers.
Update CI to build all packages and push to Cachix on merge to develop.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

.github/workflows/nix-build.yml

@@ -29,12 +29,15 @@ jobs:
           nix build .#dimentorin -o result-dimentorin
           nix build .#hackathon -o result-hackathon
           nix build .#infra -o result-infra
+          nix build .#qrcampaign -o result-qrcampaign
 
-      - name: Show build outputs
+      - name: Push to Cachix
+        if: github.event_name == 'push' && github.ref == 'refs/heads/develop'
         run: |
-          echo "Landing: $(readlink result-landing)"
-          echo "Backoffice: $(readlink result-backoffice)"
-          echo "Gacha: $(readlink result-gacha)"
-          echo "Dimentorin: $(readlink result-dimentorin)"
-          echo "Hackathon: $(readlink result-hackathon)"
-          echo "Infra: $(readlink result-infra)"
+          cachix push msdqn result-landing
+          cachix push msdqn result-backoffice
+          cachix push msdqn result-gacha
+          cachix push msdqn result-dimentorin
+          cachix push msdqn result-hackathon
+          cachix push msdqn result-infra
+          cachix push msdqn result-qrcampaign

.github/workflows/test-build.yml

@@ -1,37 +0,0 @@
-name: Test and Build
-
-on:
-  push:
-    branches: ['develop']
-  pull_request:
-    branches: ['develop']
-
-env:
-  NODE_VERSION: 22.14.0
-
-jobs:
-  build:
-    runs-on: ubuntu-latest
-
-    steps:
-      - uses: actions/checkout@v4
-
-      - name: Use Node.js ${{ env.NODE_VERSION }}
-        uses: actions/setup-node@v4
-        with:
-          node-version: ${{ env.NODE_VERSION }}
-
-      - name: Install dependencies
-        run: npm install
-
-      - name: Set env vars
-        run: |
-          echo "CMS_SECRET=${{ secrets.CMS_SECRET }}" >> $GITHUB_ENV
-          echo "CMS_STORAGE_REGION=${{ secrets.CMS_STORAGE_REGION }}" >> $GITHUB_ENV
-          echo "CMS_STORAGE_ENDPOINT=${{ secrets.CMS_STORAGE_ENDPOINT }}" >> $GITHUB_ENV
-          echo "CMS_STORAGE_ACCESS_KEY_ID=${{ secrets.CMS_STORAGE_ACCESS_KEY_ID }}" >> $GITHUB_ENV
-          echo "CMS_STORAGE_SECRET_ACCESS_KEY=${{ secrets.CMS_STORAGE_SECRET_ACCESS_KEY }}" >> $GITHUB_ENV
-          echo "CMS_POSTGRES_URL=${{ secrets.CMS_POSTGRES_URL }}" >> $GITHUB_ENV
-
-      - name: Nx Build
-        run: npx nx run-many --target=build --all