feat(inpainting): add inpainting endpoint, wire ImageGenerationFunc and return generated image URL

[gmaOCR]

Description

This patch implements an OpenAI-compatible inpainting endpoint and wires image generation into the LocalAI backend. Changes are limited to the LocalAI Go codebase.

• Adds InpaintingEndpoint handling POST /v1/images/inpainting with multipart/form-data support for image and mask.

• Endpoint writes a JSON payload with base64 image/mask and prepares a temporary output PNG path, then calls backend.ImageGenerationFunc(...) to perform generation.

• Introduces and uses the test-friendly indirection ImageGenerationFunc in image.go so the generation logic can be stubbed in tests.

• Adds unit tests for the inpainting handler (inpainting_test.go) covering missing-files and the happy path (with backend.ImageGenerationFunc stubbed).

• Registers the inpainting routes and a default model name middleware in openai.go.

• Updates Swagger (swagger.yaml) and adds a Swaggo-style docstring on the new endpoint for proper OpenAPI generation.

Notes for Reviewers

• inpainting.go (new endpoint)
• inpainting_test.go (new tests)
• image.go (ImageGenerationFunc indirection)
• mcp.go (minor related adjustments)
• openai.go (routes registration)
• swagger.yaml (OpenAPI updates)

Signed commits

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[gmaOCR]

@mudler Can i do something for [TIMEDOUT] in [It] - /Users/runner/work/LocalAI/LocalAI/core/http/app_test.go:994 @ 11/22/25 22:28:28.921 in the apple CI ? Or the problem is on CI side ?