feat: camera device with WebRTC live view

[kakopappa]

Summary

Adds a camera device with WebRTC live view in the SinricPro portal and app, plus an example that streams an ESP32 or ESP32-S3 camera over a WebRTC DataChannel. The signaling contract matches the Arduino SDK, so the existing portal and app viewers work unchanged.

It also fixes a core websocket bug that affects every device type.

The websocket fix

esp_websocket_client delivers a frame larger than its 2 KB buffer as several WEBSOCKET_EVENT_DATA events, each carrying the frame's total length and its own offset. The handler parsed every piece as a complete JSON message, so any server message above 2 KB was silently lost. A camera offer (base64 SDP plus TURN credentials) is several KB, so live view could never have worked without this.

sinricpro_frame_assembler now reassembles the pieces, up to CONFIG_SINRICPRO_MAX_MESSAGE_SIZE (16 KB). Oversized or out-of-sequence messages are dropped whole and logged once. Ping, pong and close frames are no longer passed to the JSON parser.

Changes

Area	Change
Core	sinricpro_frame_assembler; sinricpro_set_response_message(); Kconfig SINRICPRO_MAX_MESSAGE_SIZE
Camera device	sinricpro_camera with PowerState and a CameraController for getCameraCapabilities and getWebRTCAnswer
Example	examples/camera with a webrtc_camera component: session task, JPEG fragments over a DataChannel, viewer controls, automatic quality, XIAO Sense microphone
Tests	Host tests for reassembly and the camera signaling contract; base64 decode and esp_event.h shims
CI	build-camera job for esp32 and esp32s3 on ESP-IDF v5.5 and v6.1
Docs	README, API reference, CHANGELOG, example README

The SinricPro component itself gains no dependencies. esp_peer and esp32-camera are required only by the example's webrtc_camera component, which can be copied into other projects.

Testing

• test/host/run.sh: signing (23 checks), frame reassembly (14), camera signaling (18), all passing
• examples/switch rebuilt with the core changes
• examples/camera built for esp32 (1.38 MB) and esp32s3 (1.33 MB) on ESP-IDF v6.1, with no warnings in the new sources
• On hardware, an AI-Thinker ESP32-CAM viewed from the portal on the test server: offer to answer in 1.9 s, DataChannel open 4.6 s after the offer, and streaming at RSSI -78 to -85 dBm with a stable internal heap

Notes for reviewers

• The WebRTC offer callback blocks for up to about 5 s while ICE gathers, unlike other callbacks, because signaling has no trickle ICE and the answer must be complete when it is returned.
• esp32-camera 2.1.5 and later require esp_hal_clock on IDF 6.x. ESP-IDF master snapshots from before that component existed fail at configure; released IDF versions are fine.
• The camera example needs ESP-IDF 5.5 or later. esp_peer ships a prebuilt libpeer_default.a that calls esp_log(), which ESP-IDF added in 5.5, so it cannot link on older releases. CI builds the example on v5.5 (the floor) and v6.1. The SinricPro component itself keeps its existing IDF support.
• Hardware coverage so far is one board (AI-Thinker). Remote viewing through the TURN relay, a long soak, the viewer controls, and the XIAO S3 microphone are not yet exercised on hardware.
• Alexa and Google Home streaming are out of scope; they need a native H.264 track.