refactor: remove all JWT-related code and references

JWT was never used - auth uses X-User-Id header. Removes jwt.ts utility,
jsonwebtoken dependency, stubbed refresh/logout endpoints, and updates
all docs (PUML diagrams, api-routes, tex, CLAUDE.md) accordingly.

apps/server/src/utils/index.ts

@@ -1,2 +1 @@
-export * from "./jwt";
 export * from "./password";