# Feature Plan: Media Asset Normalization

## Goal
Normalize media into reusable assets so messages reference media IDs rather than duplicate transport blobs.

## Why This Fits GIA
- GIA already has shared media prep and cross-transport relay.
- Normalized assets reduce duplicate downloads/uploads and improve traceability.

## Scope
- New `MediaAsset` entity with checksum + metadata.
- New link table between `Message` and `MediaAsset`.
- De-dup by `sha256` and file size.

## Implementation
1. Add models/migrations: `MediaAsset`, `MessageMediaRef`.
2. Update inbound media ingestion to upsert `MediaAsset`.
3. Update outbound transport prep to consume `MediaAsset` references.
4. Add background backfill for existing attachments.
5. Add retention/GC strategy for orphaned assets.

## Acceptance Criteria
- Same file across transports resolves to one `MediaAsset`.
- Message records keep only pointers and display metadata.
- Relay path can reuse existing asset without re-download.

## Out of Scope
- External CDN migration in this phase.