feat: add config-file migration endpoint #1784

[KirylKurnosenka]

Adds an admin-triggered, on-demand endpoint that copies file-defined config entities into the platform blob bucket, so they become API-managed without changing what clients see or send. Supports dry-run and is idempotent on re-invocation.

Applicable issues

• fixes Slice D — Config-file migration endpoint POST /v1/admin/config/file/migrate #1784

Description of changes

• New POST /v1/admin/config/file/migrate (ConfigFileMigrateController), admin-only, migrating models/interceptors/roles/keys/routes/applications/toolsets/schemas/catalog_schemas/settings on request, with a types filter and dryRun flag.
• Reuses AdminApplyController's per-kind write pipeline (validateOnly, mutateScratch, newScratch, and a newly extracted applyEntries) instead of duplicating per-type encryption/validation/dup-checks; applyEntries and the DEPENDENCY_ORDER_COMPARATOR it now shares with applyBatch are also reused as-is by the migration endpoint.
• New SchemaMigrationNaming helper mints a deterministic canonical blob name for migrated schemas (sha256($id) + sanitized display-name slug), since a schema's canonical id is intentionally decoupled from its $id.
• Response statuses distinguish dry-run from real outcomes (migrated/skipped/failed vs. would_migrate/would_skip/would_fail) so a result can't be mistaken for an actual write.
• New ConfigFileMigrateApiTest integration coverage: happy path, idempotent re-run, dry-run (writes nothing), toolset secret round-trip, same-display-name schema disambiguation, settings migration, types filtering, invalid type (400), non-admin (403).

Notes for reviewers

• Base branch: this PR targets feat/issue-1783 (feat: short-name resolution via derivation + schema $id index #1783 #1813) rather than development, since this endpoint's presence/idempotency checks and the applySingle/EntityResult reuse depend on that branch's short-name-derivation and schema $id-alias-index work. This lets both PRs be reviewed in parallel.
• Reminder — once feat: short-name resolution via derivation + schema $id index #1783 #1813 merges: rebase this branch onto development before switching the base:

  git fetch origin
  git rebase --onto origin/development feat/issue-1783 feat/issue-1784
  git push --force-with-lease
  

  Then change this PR's base to development. This keeps the diff correct regardless of whether feat: short-name resolution via derivation + schema $id index #1783 #1813 merges as a merge commit or a squash.

Checklist

• Title of the pull request follows Conventional Commits specification

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.