Build mobile accept-and-manage flow for active queue buddy jobs

[S-Mubarak]

Description

The marketplace is incomplete unless another user can act as the buddy.

Scope

• Add accept action for open jobs
• Add active job screen with status progression
• Show requester-facing and buddy-facing views

Acceptance Criteria

• Eligible user can accept an open buddy job
• Active job screen reflects current lifecycle state
• Users only see actions allowed for their role in the job

Dependencies

Blocked by: #133
Blocked by: #134

Stack

React Native / Express

Implement backend escrow intent records for queue buddy payments

Description

Even if real Soroban escrow is deferred, the backend needs the contract boundary and payment state machine now.

Scope

• Add escrow intent model with request id, payer, buddy, amount, and state
• Generate lock/release/refund intents
• Persist transaction references and failure reasons

Acceptance Criteria

• Every accepted buddy job creates an escrow intent record
• Escrow state transitions are auditable and constrained
• API responses expose payment state to clients

Dependencies

Blocked by: #133

Stack

Express / Stellar