Add firmware artifacts, memory summary, and Doxygen gh-pages deploy

CMakeLists.txt: generate firmware.map via -Wl,-Map.

CI build job:
- Writes per-section size table to the Gitea job summary
  (visible in the Actions UI after each run).
- Uploads firmware.hex and firmware.map as a downloadable artifact
  named firmware-<sha>.

CI docs job:
- On push to main, force-pushes docs/html/ as an orphan commit to
  the gh-pages branch.  Gitea Pages must be enabled in site admin
  for the HTML to be served; the branch is always available via the
  repo file browser regardless.

.gitea/workflows/ci.yml

@@ -25,8 +25,26 @@ jobs:
       - name: Compile firmware
         run: cmake -B build -G Ninja -DCMAKE_BUILD_TYPE=MinSizeRel . && ninja -C build
 
-      - name: Print size
-        run: arm-none-eabi-size build/firmware
+      - name: Memory summary
+        run: |
+          echo '## Memory usage' >> "$GITHUB_STEP_SUMMARY"
+          echo '' >> "$GITHUB_STEP_SUMMARY"
+          echo '```' >> "$GITHUB_STEP_SUMMARY"
+          arm-none-eabi-size -A build/firmware \
+            | grep -E '^\.(text|data|bss|rodata|ARM)' \
+            >> "$GITHUB_STEP_SUMMARY"
+          echo '' >> "$GITHUB_STEP_SUMMARY"
+          arm-none-eabi-size build/firmware | tail -1 >> "$GITHUB_STEP_SUMMARY"
+          echo '```' >> "$GITHUB_STEP_SUMMARY"
+
+      - name: Upload firmware artifacts
+        uses: actions/upload-artifact@v4
+        with:
+          name: firmware-${{ github.sha }}
+          path: |
+            build/firmware.hex
+            build/firmware.map
+          if-no-files-found: error
 
   format:
     name: Check formatting
@@ -80,3 +98,19 @@ jobs:
         run: |
           doxygen Doxyfile 2>&1 | tee /tmp/doxy.log
           ! grep -q 'warning:' /tmp/doxy.log
+
+      - name: Deploy to gh-pages
+        if: github.ref == 'refs/heads/main'
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+        run: |
+          cd docs/html
+          git init -b gh-pages
+          git config user.name "ci"
+          git config user.email "ci@localhost"
+          git add -A
+          git commit -m "docs: ${GITHUB_SHA}"
+          SERVER="${GITHUB_SERVER_URL#https://}"
+          git push --force \
+            "https://x-token:${GITHUB_TOKEN}@${SERVER}/${GITHUB_REPOSITORY}.git" \
+            HEAD:gh-pages