Add version column to ci_finished_pipelines ClickHouse table

Summary

Align ci_finished_pipelines with ci_finished_builds by adding a version column to the ReplacingMergeTree definition.

Current State

Table	Engine	Version Column
ci_finished_builds	ReplacingMergeTree(version, deleted)	✅ Has version
ci_finished_pipelines	ReplacingMergeTree	❌ No version column

Why

Without a version column:

• Deduplication with FINAL relies on insertion order (non-deterministic)
• Can't use argMax(column, version) patterns reliably
• Inconsistent with ci_finished_builds

Scope

1. Add migration to add version column to ci_finished_pipelines
2. Update sync code to populate version (e.g., default now())
3. Alter ReplacingMergeTree to use the version column

Related

• #588891 (closed) (cross-partition duplicate sync events)
• !222153 (closed) (rebuild CI MVs)