fix: guard null authToken before use in surgeryAPI

[chiemezie1]

fix(surgeryAPI): fail fast when authToken is missing or invalid

PR Description

• Fix surgeryAPI.ts so the Axios request interceptor checks localStorage.getItem('authToken') before adding Authorization.
• If authToken is missing, empty, or the literal string "null", the request now throws:
  • Authentication required. Please log in to continue.
• This prevents malformed requests from sending Authorization: Bearer null to the backend.

Files changed

• surgeryAPI.ts
• surgeryAPI.test.ts

Closes: #588

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