Preserve explicit model and provider architecture (#30)

docs/implementation.md

@@ -256,3 +256,26 @@ Validation: all 115 frontend tests, app analysis, app Dart formatting, web build
 and diff checks pass. Updated existing copy expectations; telemetry tests still
 verify simulated events never count as real business success. No new click events
 were needed for this presentation-only cleanup.
+
+## Data model and provider boundaries — task #30
+
+- `architecture-30`, based on workspace PR #29. Root and frontend agent rules,
+  plus README, now explicitly preserve DTO → mapper → service → data model →
+  provider → UI across app features, shared packages, stubs and future clients.
+  Models cannot be replaced by providers or reused as transport DTOs merely
+  because their fields currently match.
+- Checked application service access: widgets compose providers with service
+  dependencies; they do not parse DTOs or invoke backend operations directly.
+  KYC and wallet transaction services already map transport data to models.
+  Auth success responses now pass through explicit response DTOs and mappers;
+  wallet profile conversion now accepts a ProfileDTO instead of a raw string.
+- Existing models, provider state, asynchronous/error behavior and public service
+  contracts are preserved. DTOs/mappers remain service implementation details.
+  No UI, telemetry semantics or backend integration changed.
+- Frontend review and validation: formatting of all 6 changed Dart files passed;
+  analysis of sxchnge_auth and sxchnge_wallet passed; all 115 frontend tests
+  passed; diff check passed. Existing service, provider and integrated tests
+  exercise the mapping paths. No additional behavioral test was needed for these
+  direct field projections. No security scan requested.
+- Stack order: KYC #21 → limits #23 → workspace #29 → this contribution;
+  retarget each dependent PR to main after its base is merged.