feat(prompt): implement interactive unknown device trust prompt and countermeasure integration - #41

…ountermeasure integration (#41)

## Summary
This PR implements the interactive user trust prompt mechanism for
unknown/unverified USB input hardware devices. When an unrecognized
keyboard connects and the policy evaluates to `PolicyAction.PromptUser`
(or `UnknownDeviceAction.PromptUser`), HIDGuard presents a modern WPF
prompt dialog allowing the user to either trust the device, immediately
block and disable the device at the PnP hardware level, or defer
judgment.

## Key Changes
- **Core Abstraction**: Created `IDevicePromptService`
(`HidGuard.Core.Trust`) providing `PromptDeviceTrustAsync` contract.
- **Countermeasure Pipeline**: Integrated `IDevicePromptService` into
`CountermeasureService.HandlePromptUserAsync`:
- Selecting **Trust** persists `DeviceTrustLevel.Trusted` to
`ITrustStore` and publishes `SecurityEventIds.DeviceReEnabled` to
Windows Event Log.
- Selecting **Block** persists `DeviceTrustLevel.Blocked` to
`ITrustStore`, disables the USB hardware node via `IDeviceDisabler`, and
publishes `SecurityEventIds.DeviceDisabled` to Windows Event Log.
- Selecting **Decide Later** retains non-disruptive state without
unauthorized trust elevation.
- **Pipeline Arrival Integration**: Updated
`KeystrokePipeline.OnDeviceConnected` to evaluate policy for newly
attached unknown keyboards and trigger prompt countermeasures.
- **WPF UI Components**:
- Implemented `DevicePromptDialog.xaml` and `.xaml.cs` styled with the
dark theme card architecture.
- Implemented `WpfDevicePromptService` with safe thread dispatching to
the WPF UI dispatcher.
- **Dependency Injection**: Registered `IDevicePromptService` as
`WpfDevicePromptService` in `App.xaml.cs`.
- **Unit Test Coverage**: Added 3 new tests in
`CountermeasureServiceTests` and 1 test in `WpfDevicePromptServiceTests`
(bringing total test count to 228 tests).
- **Documentation**: Updated test counts and test scopes in `README.md`
and `README.tr.md`.

## Verification
- `dotnet test HidGuard.sln --configuration Release` passed with 228/228
tests (100% green).
- End-to-end simulator verification passed 5/5 scenarios (`dotnet run
--project tools/HidGuard.Simulator/HidGuard.Simulator.csproj
--configuration Release --no-build -- --verify`).
- Verified zero compiler warnings under `TreatWarningsAsErrors`.

Co-authored-by: Boran <nonmr@users.noreply.github.com>