Cache expiry missing Content Length

Start by tracing the middleware's cache-expiry check and the SourceMetadataLru handling described in the issue. Compare cachedImage.ImageCacheMetadata.ContentLength with sourceImageMetadata.ContentLength, then add or update coverage for replacing an image and loading it again within the 30-second cache lifetime.

Prerequisites

• I have written a descriptive issue title
• I have verified that I am running the latest version of ImageSharp.Web
• I have verified if the problem exist in both DEBUG and RELEASE mode
• I have searched open and closed issues to ensure it has not already been reported

ImageSharp.Web version

4.0.1

Other Six Labors packages and versions

4.1.1

Environment (Operating system, version and so on)

win11

.NET version

net10

Description

The Middleware is checking the CacheLastWriteTime and SourceLastWriteTime.
I think it should also check if the Content Length differs.

        // Or has the source image changed since the image was last cached?
        if (cachedImage.ImageCacheMetadata.ContentLength == 0 // Fix for old cache without length property
            || cachedImage.ImageCacheMetadata.CacheLastWriteTimeUtc <= (DateTimeOffset.UtcNow - this.options.CacheMaxAge)
            || cachedImage.ImageCacheMetadata.SourceLastWriteTimeUtc != sourceImageMetadata.LastWriteTimeUtc)

vs

 if (cachedImage.ImageCacheMetadata.ContentLength == 0 // Fix for old cache without length property
            || cachedImage.ImageCacheMetadata.ContentLength != sourceImageMetadata.ContentLength
            || cachedImage.ImageCacheMetadata.CacheLastWriteTimeUtc <= (DateTimeOffset.UtcNow - this.options.CacheMaxAge)
            || cachedImage.ImageCacheMetadata.SourceLastWriteTimeUtc != sourceImageMetadata.LastWriteTimeUtc)

Btw. I hit an edge case eith the SourceMetadataLru cache. When you load the image, replace it and instantly load it (all in 30 seconds) --> This will result in old sourceImageMetadata because of the Lifetime of 30 seconds for the SourceMetadataLru

Steps to Reproduce

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Images

No response