fix: LinkedIn connection requests, cookie sync, and 200-char limit
- Fix send_connection_request to use correct Voyager endpoint (voyagerRelationshipsDashMemberRelationships?action=verifyQuotaAndCreateV2)
- Match LinkedIn frontend payload format exactly (inviteeUnion + memberProfile URN)
- Omit customMessage field when empty (LinkedIn rejects empty string)
- Add Content-Type: application/json header matching real browser behavior
- Fix 403 on profile GET nuking auth state for all subsequent calls
- Fix dual cookie storage sync (User table <-> SystemConfig) across 9 files
- Fix PostComposer/OnboardingWizard using wrong test-linkedin endpoint
- Enforce 200-char limit for connection notes (LinkedIn free account limit)
- Update AI prompt templates and autopilot to generate ≤200 char notes
- Add debug logging to data/connection_request_debug.log
- Add OpenTelemetry span attributes for Phoenix trace debugging