Use assets folder to store cached assets and serve them directly

[giuscris]

This pull request closes #859 by introducing changes to improve asset routing and handling, particularly for image assets. Now the generated image assets are stored in the /assets folder, allowing direct serving without php processing.

The main focus is on making the asset type explicit in routes, updating image processing paths, and preparing for future deprecations. Below are the most important changes grouped by theme:

Routing and asset handling improvements:

• Updated the assets route in routes.php to include an optional type parameter, defaulting to images, and added a where clause to restrict valid types. This makes asset type explicit and prepares for future versions where the parameter will be required.
• Added logic to AssetsController::asset to trigger a deprecation warning if the type parameter is missing and redirect requests to include type=images. This ensures backward compatibility while encouraging use of the new route format.
• Modified FileUriGenerator::generate to always include the type=images parameter when generating asset URIs, ensuring consistency with the updated route structure.

Configuration updates:

• Changed the processPath for images in system.yaml from cache/images to assets/images, aligning the configuration with the new asset management approach.

[Copilot]

Pull request overview

This PR updates Formwork’s cached image asset handling so generated images are written under /assets/images and URLs include an explicit asset type, enabling web servers to serve cached images directly (bypassing PHP) while keeping backward compatibility for legacy asset URLs.

Changes:

• Update the assets route to support an optional {type} segment (currently constrained to images) and redirect legacy requests missing type.
• Adjust image asset URI generation to always include type=images.
• Move the configured processed image output directory from cache/images to assets/images, and ignore /assets/* in git.

Reviewed changes

Copilot reviewed 4 out of 5 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
formwork/src/Files/FileUriGenerator.php	Ensures generated asset URIs include type=images to match the new route format.
formwork/src/Controllers/AssetsController.php	Adds legacy-route deprecation + permanent redirect to the typed asset route.
formwork/config/system.yaml	Moves processed image output path to ${%ROOT_PATH%}/assets/images.
formwork/config/routes/routes.php	Updates assets route path to include optional {type} and constrains allowed values.
.gitignore	Ignores generated /assets/* content in the repository.

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[Copilot]

The deprecation warning message doesn’t follow the existing deprecation-message convention in this codebase (most other E_USER_DEPRECATED messages include the version it was deprecated since). Consider updating the message to include the Formwork version when this route format became deprecated so it’s actionable when it appears in logs.

Suggested change

	trigger_error('The "assets" route without a "type" parameter is deprecated and will be removed in a future version', E_USER_DEPRECATED);
	trigger_error('The "assets" route without a "type" parameter is deprecated since Formwork 1.x and will be removed in a future version', E_USER_DEPRECATED);