fix: pass initial state via kickoff(inputs=) for CrewAI 1.10.1 compatibility

[iabshailley]

Summary

• CrewAI 1.10.1 removed the setter on Flow.state, making direct assignment (flow.state = BookingState(...)) raise TypeError: property 'state' of 'DealBookingFlow' object has no setter at runtime
• Remove the broken flow.state = ... assignment
• Pass the campaign brief via flow.kickoff(inputs={"campaign_brief": ...}) instead — the correct API for initialising flow state in CrewAI 1.10.1

Root cause

The pinned version (crewai==1.10.1, added in b80cc5d) changed Flow.state from a settable attribute to a read-only property backed by the pydantic model. Any code that assigned to it after construction broke silently at import time and raised at the first booking attempt.

Test plan

• Start buyer agent and POST to /bookings with a valid CampaignBrief
• Confirm job reaches awaiting_approval status (previously crashed immediately with TypeError)
• Confirm GET /bookings/{job_id} returns budget_allocations and recommendations
• POST /bookings/{job_id}/approve-all and confirm job reaches completed

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