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>

crates/punktfunk-host/src/capture/windows/desktop_watch.rs

@@ -1,5 +1,5 @@
 //! Input-desktop watcher (Windows) — the authoritative "normal vs secure desktop" signal for the
-//! two-process secure-desktop design (docs/windows-secure-desktop.md).
+//! two-process secure-desktop design (design/windows-secure-desktop.md).
 //!
 //! Windows switches the *input desktop* to "Winlogon" (the secure desktop) for UAC elevation, the
 //! lock screen and the login screen, and back to "Default" for the normal session. WGC captures only