Improve indices for common queries

[virajmehta]

Note

Improves claim performance and reduces table scans.

• Indexes: Adds r_*_ready (available_at, run_id) INCLUDE (task_id), w_*_ti (task_id), r_*_cei (claim_expires_at WHERE state='running'), t_*_cxlpol (task_id WHERE cancellation set with max_* ), and t_*_state_tid (state, task_id WHERE state in active/cancelled) into ensure_queue_tables.
• claim_task: Narrows pre-claim cancellation sweep to only tasks with cancellation containing max_delay or max_duration.
• Migration: Adds 20251205000000_add_claim_task_indexes.sql to redefine ensure_queue_tables and claim_task, and applies updated indexes/functions to all existing queues.

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