feat: unified axes panel, language selector cleanup, filament mismatch detection, Spoolman slot assignment

- Merged XY + Z axis cards into single Axes Control panel with shared step
  size row and free-text mm input; Home XY/Z placed below respective pads;
  Home All + Motors Off centred at bottom
- Language selector removed from header bar, now only in Settings → Appearance
- Upload-and-Print blocked on GCode/AMS material mismatch; slot mapper dialog
  opens automatically with mismatch warning highlighting affected slots
- Spoolman spool-per-slot assignment: dropdown in AMS status tab per kachel,
  dedicated card in Filaments settings tab with save button
- nightly.yml: NIGHTLY_CHANGELOG.md takes precedence over auto-generated
  commit log when present; CI uses it as release body verbatim

.gitea/workflows/nightly.yml

@@ -113,18 +113,23 @@ jobs:
             | grep -E '^v[0-9]+\.[0-9]+\.[0-9]+$' | head -1)
           [ -z "$PREV_TAG" ] && PREV_TAG=$(git rev-list --max-parents=0 HEAD)
 
-          # Changelog generieren — nur feat/fix, keine ci/release/build-Scopes
+          # Changelog: NIGHTLY_CHANGELOG.md hat Vorrang (manuell gepflegt),
+          # sonst auto-generiert aus feat/fix-Commits seit letztem Stable-Tag
           BODY_FILE=$(mktemp)
           printf '## KX-Bridge %s — Nightly Build\n\n' "$VERSION" > "$BODY_FILE"
           printf '[experimental] Untested features, for testers only.\n\n' >> "$BODY_FILE"
-          printf '### Changes since `%s`\n\n' "$PREV_TAG" >> "$BODY_FILE"
-          git log "${PREV_TAG}..HEAD" --pretty=format:'%s' --no-merges \
-            | grep -E '^(feat|fix)[:(]' \
-            | grep -Ev '^(feat|fix)\((ci|release|build|workflow)\)' \
-            | sed 's/^/- /' \
-            >> "$BODY_FILE" || true
-          if ! grep -q '^- ' "$BODY_FILE"; then
-            printf '- No user-facing changes in this build\n' >> "$BODY_FILE"
+          if [ -s NIGHTLY_CHANGELOG.md ]; then
+            cat NIGHTLY_CHANGELOG.md >> "$BODY_FILE"
+          else
+            printf '### Changes since `%s`\n\n' "$PREV_TAG" >> "$BODY_FILE"
+            git log "${PREV_TAG}..HEAD" --pretty=format:'%s' --no-merges \
+              | grep -E '^(feat|fix)[:(]' \
+              | grep -Ev '^(feat|fix)\((ci|release|build|workflow)\)' \
+              | sed 's/^/- /' \
+              >> "$BODY_FILE" || true
+            if ! grep -q '^- ' "$BODY_FILE"; then
+              printf '- No user-facing changes in this build\n' >> "$BODY_FILE"
+            fi
           fi
           printf '\n\n---\n\n### Update Docker image\n\n```bash\ndocker compose pull && docker compose up -d\n```\n\n' >> "$BODY_FILE"
           printf 'Image tag: `gitea.it-drui.de/viewit/kx-bridge:nightly`\n' >> "$BODY_FILE"