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>

web/Dockerfile

@@ -1,6 +1,6 @@
 # punktfunk management console — TanStack Start built with Bun, served by the Nitro `bun`
 # preset bundle. Build context is the REPO ROOT (orval generates the API client from
-# docs/api/openapi.json, referenced as ../docs/api/openapi.json from web/):
+# api/openapi.json, referenced as ../api/openapi.json from web/):
 #
 #   docker build -f web/Dockerfile -t punktfunk-web .
 #
@@ -15,7 +15,7 @@ WORKDIR /repo/web
 COPY web/package.json web/bun.lock ./
 RUN bun install --frozen-lockfile --ignore-scripts
 
-COPY docs/api/openapi.json /repo/docs/api/openapi.json
+COPY api/openapi.json /repo/api/openapi.json
 COPY web/ ./
 # prebuild runs orval (openapi → src/api/gen); the paraglide vite plugin compiles i18n.
 RUN bun run build