Geo - Replicate PersonalSnippet uploads

What does this MR do and why?

Add Geo SSF (self-service framework) replication and verification for the snippet_uploads partition table (PersonalSnippet model), so personal snippet attachments are mirrored from the primary to secondary Geo sites alongside other upload types.

Generated with scripts/geo/generate-blob-replicator and adjusted for PersonalSnippet specifics:

• Shorten Postgres identifiers for the t.references unique index on the state table and the FK unique index on the registry (ps_upload alias) to fit the 63-character limit.
• registry_consistency_worker_spec patch fixed to use the correct factory name :geo_personal_snippet_upload (generator emitted :geo_personal_snippet).

Selective sync uses the organization_id sharding key directly via the parent factory's organization: keyword — no parent-hierarchy workaround needed (unlike #589912 (closed) and #589904 (closed)).

Replication is gated by the ops feature flag geo_personal_snippet_upload_replication (default disabled); flipping it on for general availability is tracked separately under the parent epic.

Changelog: added EE: true

References

• Relates to #589914 (closed)
• Parent epic: gitlab-org#20933 (per-upload-partition Geo replication)

How to set up and validate locally

Validation requires a local Geo setup (primary + secondary), and make sure you run geo migrations with: rails db:migrate:geo. Then:

1. On the primary, enable the feature flag:

   Feature.enable(:geo_personal_snippet_upload_replication)

2. Create a personal snippet with an attached file (via the snippets UI or in the Rails console).

3. On the secondary, watch the registry get populated:

   Geo::PersonalSnippetUploadRegistry.last

   Confirm it transitions through `pending → started → synced` and that `verification_state` reaches `succeeded`.

4. Confirm the file exists on the secondary's object storage / disk at the same path as the primary.

5. Spot-check the GraphQL API:

   {
     geoNode(name: "<secondary-name>") {
       personalSnippetUploadRegistries { nodes { id state } }
     }
   }

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