Add SP Pool replication policy mechanism

[anjor]

Summary

• Adds an SP Pool feature for Milestone 2: users assign preparations + storage providers with a per-provider replication policy (e.g. {"market": 1, "pdp": 1}), and the system auto-generates/manages Schedules to match the desired state
• New models: SPPool, SPPoolProvider, SPPoolPreparation with ReplicationPolicy custom JSON type (stored as map[DealType]int)
• Inline reconciliation engine computes the cross-product of providers × preparations × policy deal types, creates missing schedules, and pauses/unlinks stale ones
• 11 REST API endpoints under /api/sp-pool with full CRUD, pause/resume, and provider/preparation management
• 11 CLI commands under singularity deal sp-pool
• SPPoolProviderID FK added to Schedule (SET NULL on delete) to track which schedules are pool-managed

Test plan

• go build ./... — compiles clean
• go vet ./... — no issues
• go test ./model/... ./handler/... ./api/... — all pass
• Reconciliation tests: cross-product (2 providers × 2 preps × mixed policy → 6 schedules), idempotency, paused pool creates paused schedules, policy change unlinks removed deal types, empty pool is no-op
• Handler tests: create validation (name required, duplicate rejected, cron rules), add-preparation validation (wallet required, duplicate rejected, not-found pool)
• Manual end-to-end: create pool → add provider with policy → add preparation → verify schedule auto-created → pause/resume → remove provider → verify schedule unlinked
• Swagger regeneration (go generate ./...) after merge

[anjor]

Re-scoped this PR per review feedback. The SP Pool machinery is gone; the branch now just adds a string group label on schedules, --group on schedule create/update, and a deal schedule create-batch command for the cross-product and replication expansion logic. Full repo test pass is green after codegen (go test ./...).