Percent-encoded non-ASCII image hrefs are not resolved against resources-dir

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## Description

`resvg` does not resolve a local `` resource when the image filename is UTF-8 percent-encoded. This is a practical compatibility issue because SVG editors such as Inkscape may save non-ASCII local filenames in percent-encoded form.

The same local image resolves when the href uses the decoded Unicode filename directly.

## Minimal reproduction

Directory layout:

```text
repro/
url-encoded-image-href.svg
decoded-image-href.svg
images/
细节3-mine.png
```

`url-encoded-image-href.svg`:

```xml

```

`decoded-image-href.svg` is identical except the href is decoded:

```xml

```

`images/细节3-mine.png` can be any valid PNG file.

## Commands run

```powershell
resvg --version
resvg --resources-dir .\repro .\repro\url-encoded-image-href.svg .\repro\cli-encoded.png
resvg --resources-dir .\repro .\repro\decoded-image-href.svg .\repro\cli-decoded.png
```

## Actual behavior

The percent-encoded href emits a warning and the external image is not rendered:

```text
0.47.0
Warning (in usvg::parser::image:110): 'images/%E7%BB%86%E8%8A%823-mine.png' is not a path to an image.
```

In my local reproduction, the encoded output PNG was much smaller than the decoded output, consistent with the child image being omitted:

```text
cli-encoded.png 370 bytes
cli-decoded.png 2267 bytes
```

## Expected behavior

Since `href` is URL/IRI-like and `--resources-dir` is used for resolving relative resources, `resvg` should percent-decode local relative image hrefs before resolving them against `resources_dir`. The encoded href:

```text
images/%E7%BB%86%E8%8A%823-mine.png
```

should resolve to the existing local file:

```text
images/细节3-mine.png
```

## Environment

- `resvg` CLI: `0.47.0`
- OS: Windows

Start by reproducing the issue with the two SVG files and the resvg CLI commands using --resources-dir, then inspect the image-resolution path indicated by the usvg::parser::image warning. Verify that the percent-encoded local href resolves to the existing UTF-8 filename and that the encoded and decoded inputs render the external image consistently.

Written by the indexing model from the issue text.