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/main.rs

@@ -389,7 +389,7 @@ fn real_main() -> Result<()> {
         }
         // USER-session WGC helper (Windows two-process secure-desktop design): capture the EXISTING
         // SudoVDA via WGC + NVENC, stream AUs on stdout to the SYSTEM host. Spawned by the host
-        // (CreateProcessAsUser), not run by hand. See docs/windows-secure-desktop.md.
+        // (CreateProcessAsUser), not run by hand. See design/windows-secure-desktop.md.
         #[cfg(target_os = "windows")]
         Some("wgc-helper") => {
             let get = |flag: &str| {
@@ -704,7 +704,7 @@ SPIKE OPTIONS:
 
 NOTES:
     'portal' needs headless Sway + xdg-desktop-portal-wlr running in this session
-    (see docs/linux-setup.md). 'synthetic' needs no capture session and always runs.
+    (see design/linux-setup.md). 'synthetic' needs no capture session and always runs.
     Encoded AUs are written to a playable file AND (unless --no-loopback) fed through a
     punktfunk_core host→client loopback that reassembles and byte-verifies each one.
     Both 'serve' and 'punktfunk1-host' advertise the native service over mDNS