[APIView] Epic: Version Entity & Data Migration

[tjprescott]

Overview

Foundation work for the APIView Version-Centric Data Model. Introduces the APIVersion entity, wires it into all upload paths, and backfills historical data.

Work Items

• [APIView] WI-1: APIVersion Entity & Repository Layer #14992 — WI-1: APIVersion Entity & Repository Layer
• [APIView] WI-2: Wire Upload Paths #14993 — WI-2: Wire Upload Paths
• [APIView] WI-3: Backfill Revisions & Samples #14994 — WI-3: Backfill Revisions & Samples

Dependency Chain

WI-1 → WI-2 → WI-3

WI-1 has no dependencies and is the starting point for the entire version-centric model. WI-3 is a prerequisite for most downstream work (Retention, Comments, PR Lifecycle, Approvals).