Add optional GATT service compliance validation after device discovery

[RonanB96]

Library gap

BaseGattService.validate_service() can check required/optional/conditional characteristics against a discovered set, but Device.discover_services() never runs compliance checks. Consumers scanning unknown devices get UUID→class mapping only, with no “is this Battery Service missing 0x2A19?” feedback.

Profiles are not readable as bytes — compliance is inferred from discovered service/characteristic UUID sets (see research in docs/codebase/CONCERNS.md).

Background (citations)

• Service validation API: src/bluetooth_sig/gatt/services/base.py (validate_service, validate_bluetooth_sig_compliance)
• Discovery today: src/bluetooth_sig/device/connected.py (discover_services) — caches services/chars, no validation
• Example service with required/optional maps: src/bluetooth_sig/gatt/services/environmental_sensing.py
• Permitted-characteristic YAML exists but is not wired to runtime: bluetooth_sig/assigned_numbers/profiles_and_services/ess/ess_permitted_characteristics.yaml, src/bluetooth_sig/registry/profiles/permitted_characteristics.py

Suggested approach

1. Add an optional API on Device (or helper on translator/service layer), e.g. validate_discovered_services() -> list[ServiceValidationResult], invoked after discover_services().
2. Build validation input from discovered UUID sets (no extra BLE reads required).
3. Return structured, human-readable issues (missing mandatory chars, unexpected extras) using existing ServiceValidationResult types if available.
4. Do not auto-run on every connect — opt-in to avoid overhead.

Out of scope

• Wiring PermittedCharacteristicsRegistry into hot path (optional future enhancement)
• BLE transport / reading characteristic values during validation

Acceptance criteria

• Opt-in validation API documented in docs/source/how-to/usage.md or ble-integration.md
• Tests with mocked discovery data: compliant Battery Service + non-compliant case (missing Battery Level)
• just qa passes

Key files to read first

• src/bluetooth_sig/device/device.py
• src/bluetooth_sig/gatt/services/base.py
• src/bluetooth_sig/types/ (search ServiceValidationResult)
• tests/device/ for Device test patterns

Consumer value

Helps apps answer “what does this device expose?” without deep GATT knowledge — aligned with library mission (docs/source/explanation/what-it-solves.md).