feat: add membership_type column to storage_module for multi-scope storage

[pyramation]

Summary

Updates the storage_module table schema to support multi-scope (multi-tenant) storage. This syncs the published metaschema-modules package with the schema changes already merged in constructive-db (PR #876).

Changes to storage_module/table.sql:

1. New column membership_type int DEFAULT NULL — discriminates storage scope:

   • NULL = app-level storage (gated by AuthzMembership via app_sprt)
   • Non-NULL = entity-scoped storage (gated by AuthzEntityMembership, value matches the entity's membership type)

2. Renamed default table names — buckets/files/upload_requests → app_buckets/app_files/app_upload_requests to clearly identify database-level (app-scope) storage tables vs entity-scoped ones.

3. New unique index storage_module_unique_scope on (database_id, COALESCE(membership_type, -1)) — enforces at most one storage module per scope per database (one app-level + one per membership type).

Why: constructive PR #1009 adds multi-scope bucket resolution to the GraphQL plugins, which queries storage_module.membership_type. CI fails because the published package doesn't have this column yet. Publishing this update unblocks that PR.

Review & Testing Checklist for Human

• Verify the schema matches constructive-db exactly — compare this file against constructive-db/pgpm-modules/metaschema-modules/deploy/.../storage_module/table.sql on main to confirm no drift
• Confirm the default name rename is intentional — changing from 'buckets'/'files'/'upload_requests' to 'app_buckets'/'app_files'/'app_upload_requests' affects all newly provisioned databases
• Validate the COALESCE(-1) sentinel — the unique index uses COALESCE(membership_type, -1) to treat NULL as a distinct value; confirm -1 will never be a valid membership_type

Notes

• Verify and revert scripts are unchanged — verify_table() still works since the table name hasn't changed, and revert is a DROP TABLE.
• This is a CREATE TABLE deploy script, not an ALTER TABLE migration. Existing databases will need a separate migration to add the column and index.

Link to Devin session: https://app.devin.ai/sessions/18879be982854a40abe5c9b915aa4a84
Requested by: @pyramation

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