## Motivation
- Image editing previously ignored input image dimensions, always
defaulting to 1024x1024
- Size dropdown was hidden in edit mode, giving users no control over
output dimensions
- Portrait/landscape presets used non-standard aspect ratios (1024x1365
/ 1365x1024)
## Changes
- Added "auto" size option that uses input image dimensions for edits,
defaults to 1024x1024 for generation
- Introduced ImageSize Literal type and normalize_image_size() validator
(replaces raw str size fields)
- Updated portrait/landscape presets to standard 1024x1536 / 1536x1024
- Made size selector visible in edit mode (previously hidden)
- Default size changed from "1024x1024" to "auto"
## Why It Works
- "auto" reads actual input image dimensions via PIL at generation time,
so edits preserve the original aspect ratio
- Pydantic field_validator on both ImageGenerationTaskParams and
ImageEditsTaskParams normalizes None → "auto", keeping the API
backward-compatible
## Test Plan
### Manual Testing
- Verify image edits output at the input image's native resolution when
size is "auto"
- Verify size dropdown appears and works in both generate and edit modes
ciaranbor
f54c80b121
