Feature — Global Kill-Switch

[coderkrp]

As a trader,
I want a global kill-switch,
So that I can instantly halt all trading activity in emergencies.

Acceptance criteria

• AC1: A secure API endpoint (e.g., POST /api/v1/killswitch) is created to enable or disable the kill-switch.
• AC2: When the kill-switch is active, all new order placement requests are immediately rejected with an HTTP 423 Locked status and a clear error message.
• AC3: Existing in-flight requests are allowed to complete.
• AC4: The state of the kill-switch is persisted to the database to survive application restarts.
• AC5: The current state of the kill-switch is reported in the /status endpoint.

Definition of Done

• Code implemented in a feature/fix branch
• Unit / integration tests added or existing tests updated
• Linting passed and code builds locally
• Docs / README updated if behavior changed
• PR opened and linked (Closes #<issue-number>)
• Manual QA steps verified (if applicable)