accept object or JSON string for filters query param

[ved015]

Summary

• Fixes a mismatch where filters was documented/used as an object but validated as a string
• ListMemoriesQuerySchema.filters now accepts either
  • a structured filters object or
  • a JSON encoded string
• OpenAPI metadata updated with examples for both shapes

What changed

• Added SearchFiltersParamSchema (union of object + JSON string -> parsed object) validated via SearchFiltersSchema
• Updated ListMemoriesQuerySchema.filters to use SearchFiltersParamSchema

@Dhravya @MaheshtheDev please have a look

[ved015]

FYI the Claude Code Review workflow is failing on this PR because it is from a fork.
I check and since the action tries to fetch a GitHub OIDC token, but for pull_request runs from forks idts GitHub provides the OIDC env vars / secrets so it fails

[ved015]

@claude review