BM-2430: Add status filter to list_requests and fix pagination cursor bug

[willpote]

Adds a status query parameter to the GET /v1/market/requests endpoint allowing filtering by request status (submitted, locked, fulfilled, expired). Also fixes a pagination cursor bug that could cause records to be silently dropped during pagination.

Changes

• Add status filter parameter to list_requests DB function and the /v1/market/requests API endpoint, with corresponding SQL queries for all cursor/status combinations
• Fix RequestCursor.request_digest formatting: B256::to_string() produces 0x-prefixed hex but the DB stores plain hex, causing string comparison mismatches in the pagination WHERE request_digest < $cursor clause. This silently drops records when multiple entries share the same timestamp and their digests start with hex chars > 0. Fixed in all 3 cursor construction sites (market.rs, requestors.rs, provers.rs)
• Add test_list_requests_pagination_same_timestamp DB unit test that reproduces the cursor formatting bug
• Add test_list_requests_with_status_filter DB unit test for the new status filter
• Add test_market_requests_pagination_completeness API integration test that verifies no records are lost during one-by-one pagination
• Add DB index on (request_status, created_at) to support filtered queries

Made with Cursor

[linear]

BM-2430 Add status filter to list_requests and fix pagination cursor bug