fix(workflows): migrate per-node inventory/environment overrides

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Bug and impact

PR #4024 (workflow params) introduced migration 2.19.11, which moved per-node Ansible limit values into project__task_params but did not migrate inventory_id or environment_id from legacy project__workflow_node columns.

Impact: On upgrade, any workflow node with per-node inventory or environment overrides (supported since v2.18.15) silently loses those settings. Tasks spawned from affected nodes run with the template defaults instead of the configured overrides — a data-loss bug with direct user-facing breakage.

Trigger scenario:

1. User configures a workflow node with a custom inventory and/or environment (no limit override).
2. Instance upgrades to a build containing PR feat/workflow params #4024.
3. Migration 2.19.11 runs; task_params_id stays NULL because the node has no limit.
4. The application no longer reads the legacy columns; overrides are gone.

Backup/restore was also affected: pre-2.19.11 backups stored inventory/environment by name on workflow nodes, but restore no longer mapped those fields into TaskParams.

Root cause

WorkflowNode was refactored from direct InventoryID/EnvironmentID/Limit fields to TaskParams, but migration_2_19_11 PostApply only queried nodes with non-empty limit and only copied the limit JSON into task_params.

Fix

• 2.19.11: Migrate all three override types (limit, inventory, environment) into project__task_params.
• 2.19.12: Idempotent repair migration for databases that already ran the buggy 2.19.11 (backfills inventory/environment into existing or new task_params rows).
• Backup restore: Re-read deprecated top-level inventory/environment name fields from pre-2.19.11 backups into TaskParams.

Validation

• go test ./db/sql/... -run TestMigration_2_19 — pass (limit, inventory/environment, partial-migration repair)
• go test ./services/project/... — pass