feat: webp native (pure-go) implementation

[skrashevich]

This pull request adds native WebP snapshot and streaming support to the project, enabling both single-frame (/api/frame.webp) and multipart streaming (/api/stream.webp) endpoints for WebP images. The implementation uses pure Go (via the (go-webp library), allowing for efficient, dependency-free WebP encoding and decoding. The changes include the core WebP API, HTTP handlers, codec conversion utilities, and documentation updates.

Key changes:

WebP API and HTTP Endpoints:

• Implements a new internal/webp package providing /api/frame.webp (snapshot) and /api/stream.webp (multipart stream) endpoints, including request handling, caching, and transcoding from H264/H265/JPEG to WebP. (internal/webp/webp.go, internal/webp/webp.goR1-R160)
• Registers the WebP API in main.go and updates OpenAPI documentation and web UI links to reflect the new endpoints. (main.go, [1] [2]; website/api/openapi.yaml, [3] [4]; www/links.html, [5]

WebP Codec Support and Conversion Utilities:

• Adds a new pkg/webp package with helpers for encoding/decoding WebP, converting JPEG and RAW frames to WebP, and handling multipart WebP streaming. (pkg/webp/consumer.go, [1]; pkg/webp/helpers.go, [2]; pkg/webp/rtp.go, [3]; pkg/webp/writer.go, [4]
• Updates the image producer to detect and convert WebP images to JPEG when necessary, ensuring compatibility with existing pipelines. (pkg/image/producer.go, [1] [2] [3] [4]

Dependency and Schema Updates:

• Adds the go-webp library as an indirect dependency for pure Go WebP support and updates the Go version requirement. (go.mod, [1] [2]
• Updates the configuration schema to include WebP options and logging. (www/schema.json, [1] [2]

Testing:

• Introduces comprehensive tests for WebP encoding/decoding and the new API initialization. (internal/webp/webp_test.go, [1]; pkg/webp/webp_test.go, [2]

These changes collectively provide efficient, modern image streaming capabilities with broad browser support and no external dependencies for WebP processing.

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  Binary Size Comparison Tool
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Current branch: go-webp

Building master branch...
Building go-webp branch...

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  Results
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  Branch                        Size   Size (MB)
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  master                    18791890    17.92 MB
  go-webp                   19044098    18.16 MB

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  Difference:           +246.2 KB (+1.34%)
                       (≈ +0.24 MB)

✓ Binary size change is minimal