fix(data-types): migrate sync to v3 signatures API

[r0ny123]

Problem

The plugin still uses the deprecated v2 function-data-types operations for importing remote types and propagating local function changes. The current API contract exposes v3 signature operations instead, with analysis-scoped type identifiers and grouped type definitions. The old response models therefore cannot be used as a direct replacement.

Change

• Add a small adapter over the bundled SDK client's raw request layer.
• Fetch signatures in batches through GET /v3/functions/signatures.
• Resolve the v3 type graph into the legacy models consumed by the existing IDA importer.
• Update function headers through PUT /v3/analyses/{analysis_id}/functions/{function_id}/signature.
• Treat has_signature=false as an unavailable signature rather than a reason to push an old data-type blob back to the service.
• Skip stack-variable writes explicitly because the current v3 contract has no stack-variable update operation.
• Add coverage for conversion, type-ID resolution, function updates, no-op paths, and API failures.

The change is deliberately contained at the service boundary: the existing importer and the rest of the plugin can continue using their established legacy model objects while the bundled SDK remains compatible with the other plugin services.

Fixes #174.

Validation

• pytest --confcutdir=tests/unit/data_types tests/unit/data_types/test_v3_adapter.py -q — 3 passed
• ruff check reai_toolkit/app/services/data_types/data_types_service.py reai_toolkit/app/services/data_types/v3_data_types.py reai_toolkit/app/services/variable_sync/variable_sync_service.py tests/unit/data_types/test_service.py tests/unit/data_types/test_v3_adapter.py tests/unit/variable_sync/test_service.py
• python -m py_compile reai_toolkit/app/services/data_types/data_types_service.py reai_toolkit/app/services/data_types/v3_data_types.py reai_toolkit/app/services/variable_sync/variable_sync_service.py tests/unit/data_types/test_service.py tests/unit/data_types/test_v3_adapter.py tests/unit/variable_sync/test_service.py
• git diff --check

The broader service tests require IDA's embedded runtime modules and were not runnable in the standalone checkout used for this change.