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/orval.config.ts

@@ -2,11 +2,11 @@ import { defineConfig } from "orval";
 
 // Generates a typed React Query client from the host's checked-in OpenAPI document.
 // Regenerate after any management-API change: `pnpm api:gen` (the Rust side regenerates
-// docs/api/openapi.json via `cargo run -p punktfunk-host -- openapi`).
+// api/openapi.json via `cargo run -p punktfunk-host -- openapi`).
 export default defineConfig({
 	punktfunk: {
 		input: {
-			target: "../docs/api/openapi.json",
+			target: "../api/openapi.json",
 		},
 		output: {
 			mode: "tags-split",