fix: complete the docs/→design/ and openapi→api/ rename references

The file moves (docs/ → design/, docs/api/openapi.json → api/openapi.json) landed
in d01a8fd, but the matching reference updates did not — so mgmt.rs's drift-test
`include_str!("../../../docs/api/openapi.json")` pointed at a path that no longer
exists and the host failed to build. This restores it and updates every reference:

  - mgmt.rs include_str! → ../../../api/openapi.json (fixes the build)
  - web/orval.config.ts codegen target, web/Dockerfile, .dockerignore
  - deb/rpm/Arch packaging install paths
  - CLAUDE.md, the .gitea CI workflows, code doc-comments, design-doc cross-links

docs-site route URLs (/docs/...) untouched.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

scripts/bootstrap-ubuntu.sh

@@ -205,5 +205,5 @@ cat <<'NEXT'
        export XDG_RUNTIME_DIR=/run/user/$(id -u) WAYLAND_DISPLAY=wayland-1
        swaymsg -t get_outputs                         # confirm HEADLESS-1
        bash scripts/headless/capture-smoke-test.sh    # wf-recorder -> hevc_nvenc -> /tmp/*.mkv
-  5. Then start M0 proper: see docs/linux-setup.md.
+  5. Then start M0 proper: see design/linux-setup.md.
 NEXT