Migrate device endpoints to generated models

[gpunto]

Goal

Migrate the /devices endpoints to generated models. Part of the incremental OpenAPI model migration.

Built on top of the Serializer foundation PR (this is the first slice with a generated enum, PushProvider).

Part of AND-1291

Implementation

• Add generated DeviceResponse, ListDevicesResponse, and CreateDeviceRequest (with the typed PushProvider sealed enum); delete the hand-written DeviceDto, DevicesResponse, and AddDeviceRequest.
• Register CreateDeviceRequest.PushProvider.PushProviderAdapter() in Serializer (the one-line-per-enum pattern the foundation enables).
• Point DeviceApi/MoshiChatApi/mappers at the generated types (real names, no aliases); Device.toDto() supplies placeholder createdAt/userId (required by the generated model, ignored by the server on upstream payloads).

Testing

• Project-wide spotlessApply, apiDump (no API drift), lint, detekt, and testDebugUnitTest all pass.
• Verified on device: addDevice (generated request + PushProvider enum) succeeds, getDevices parses 22 real DeviceResponses (roundTrip=true), deleteDevice succeeds.

[github-actions]

PR checklist ✅

All required conditions are satisfied:

• Title length is OK (or ignored by label).
• At least one pr: label exists.
• Sections ### Goal, ### Implementation, and ### Testing are filled, or the PR is bot-authored.
• An issue is linked (Linear ticket or GitHub issue), or the PR is bot-authored.

🎉 Great job! This PR is ready for review.

[github-actions]

SDK Size Comparison 📏

SDK	Before	After	Difference	Status
stream-chat-android-client	5.93 MB	5.94 MB	0.01 MB	🟢
stream-chat-android-ui-components	11.20 MB	11.20 MB	0.01 MB	🟢
stream-chat-android-compose	12.66 MB	12.67 MB	0.01 MB	🟢

[sonarqubecloud]

Quality Gate failed

Failed conditions
61.2% Coverage on New Code (required ≥ 80%)

See analysis details on SonarQube Cloud