Migrate dashboard to generated GraphQL types and enum constants

Replace all manual GraphQL document imports from src/graphql/* with
generated TypedDocumentNode imports from @/gql/graphql, and replace
all hardcoded enum string comparisons with generated enum constants
for type safety. Delete the old manual GraphQL files.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>