fix(session): consistent client identification for session lifecycle

[zortos293]

Summary

Fixes session polling 500 errors by ensuring consistent client identification (nv-client-id and x-device-id) across the entire session lifecycle. Previously, each API call generated new random UUIDs, causing the server to reject poll requests as coming from a different client.

Changes

Session lifecycle identification

• createSession now generates clientId and deviceId once and returns them in SessionInfo
• pollSession and stopSession accept and reuse the same identifiers from session creation
• Added clientId/deviceId fields to SessionInfo, SessionPollRequest, and SessionStopRequest interfaces in src/shared/gfn.ts

Header normalization

• Refactored requestHeaders to accept options object with clientId, deviceId, and includeOrigin flags
• Poll requests now omit Origin and Referer headers (matching claimSession pattern)
• getActiveSessions and claimSession prefetch/validation calls updated to use new signature

Renderer integration

• App.tsx now passes clientId and deviceId from SessionInfo to pollSession and stopSession calls