[edwin-hollen]

Adds golden widget and edge-case tests in flutter_svg for SVG <filter> support (feGaussianBlur, feOffset, feMerge, feMergeNode), and updates dependency constraints to vector_graphics: ^1.3.0, vector_graphics_codec: ^1.2.0, and vector_graphics_compiler: ^1.3.6.

Follow-up to #11909
Fixes flutter/flutter#158592

Added Golden Tests

• filter.gaussian_blur.png: Isotropic feGaussianBlur (stdDeviation="4").
• filter.offset.png: feOffset (dx="20", dy="15").
• filter.drop_shadow.png: Multi-primitive drop shadow (feGaussianBlur on SourceAlpha, feOffset, feMerge).
• filter.gradient_drop_shadow.png: Drop shadow on a shape filled with a linearGradient.
• filter.group_opacity.png: <g filter="url(#...)" opacity="0.5"> compositing a multi-layer filter once under group opacity.
• filter.anisotropic_blur.png: Directional feGaussianBlur (stdDeviation="12 1").
• filter.scaled_transform.png: Drop shadow under <g transform="scale(2)"> scaling blur and offset proportionally.

Also adds widget tests for stdDeviation="0", negative feOffset (dx/dy), and mixed unsupported filter fallback (feFlood + feGaussianBlur).

Pre-launch Checklist

• I read the Contributor Guide and followed the process outlined there for submitting PRs.
• I read the Tree Hygiene page, which explains my responsibilities.
• I read and followed the relevant style guides and ran the auto-formatter.
• I signed the CLA.
• I listed at least one issue that this PR fixes in the description above.
• I updated/added relevant documentation (doc comments with ///).
• I added new tests to check the change I am making, or this PR is test-only.
• I wrote epic tests if I helped fix a bug or made a change.
• All existing and new tests are passing.

[gemini-code-assist]

Code Review

This pull request updates flutter_svg to version 2.4.1, adding support for SVG filters including feGaussianBlur, feOffset, and feMerge. It bumps the versions of vector_graphics, vector_graphics_codec, and vector_graphics_compiler in pubspec.yaml, and adds a new group of widget tests in widget_svg_test.dart to verify the correct rendering and fallback behavior of these filters. There are no review comments, and I have no feedback to provide.