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/session_tuning.rs

@@ -9,7 +9,7 @@
 //! Raw C-ABI FFI (winmm/kernel32/dwmapi/avrt) rather than the `windows` crate so it builds without
 //! pulling new windows-rs features. No-op on non-Windows. Per-thread effects (MMCSS, execution
 //! state) auto-revert at thread exit (= session end); the process-wide bits revert at process exit.
-//! See `docs/host-latency-plan.md` Tier 3A.
+//! See `design/host-latency-plan.md` Tier 3A.
 
 // Every `unsafe` block in this file carries a `// SAFETY:` proof; enforce it (unsafe-proof program).
 #![deny(clippy::undocumented_unsafe_blocks)]