Rebuild the site as a terminal-style agent on Astro

Replace the single Gatsby page with a dark, terminal-style agent that answers
questions about Dennis's work from one curated knowledge base. There is no
model and no network call, so answers cannot be invented. A plain "Classic
view" and an optional light theme sit one click away.

Site
- Terminal UI (React island): typed answers, tool-call lines, slash commands,
  autocomplete, history, deep links, a short /oncall game
- Content focused on what recruiters scan for; personal and employer-internal
  details are left out
- No profile photo anywhere, including the new link-preview card and icons
- Corrected facts from the old page (dates, titles, tenses, skill tiers)

Tooling
- Migrate Gatsby 5 to Astro 7 (Node 22.23+); builds in about 1 second
- Self-host fonts, so visitors make no request to third parties
- Link-preview card, favicon set, web manifest and a service-worker clean-up
  for returning visitors
- Deploy workflow builds with npm ci on Node 22 and uploads dist/
- Track package-lock.json

Quality
- Tests for routing and for markup injection from visitor input
- A content guard scans every reachable answer; the list of things that must
  never be published lives in a git-ignored local file

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

.gitea/workflows/workflow.yaml

@@ -16,21 +16,23 @@ jobs:
       - name: Set up Node.js
         uses: actions/setup-node@v4
         with:
-          node-version: 20
+          node-version: 22
+          # Astro needs Node 22.23 or newer; runner images can cache an older 22.x.
+          check-latest: true
 
       - name: Install dependencies
-        run: npm install --legacy-peer-deps
+        run: npm ci
 
-      - name: Build Gatsby site
-        run: npx gatsby build
+      - name: Build Astro site
+        run: npm run build
         env:
           NODE_ENV: production
           CI: true
 
       - name: Check build output
         run: |
-          if [ ! -d "public" ]; then
-            echo "Build failed - public directory not found"
+          if [ ! -f "dist/index.html" ]; then
+            echo "Build failed - dist/index.html not found"
             exit 1
           fi
 
@@ -55,7 +57,7 @@ jobs:
             --exclude='mailadmin/' \
             --exclude='postfixadmin/' \
             --exclude='roundcube/' \
-            public/ \
+            dist/ \
             $DEPLOY_USER@$DEPLOY_HOST:$DEPLOY_PATH
 
       - name: Verify deployment