Implement remaining SVG filter primitives (long-tail coverage)

[FlorianRappl]

Description
A number of SVG filter primitives remain unsupported, limiting SVG effect compatibility.

Scope

• Inventory currently unsupported filter primitives.
• Implement remaining primitives incrementally in renderer/filter pipeline.
• Ensure composability between primitives and sensible fallback behavior.

Acceptance criteria

• Additional primitives move from unsupported to supported with test coverage.
• Representative real-world SVG samples render closer to browser output.
• Remaining unsupported primitives (if any) are explicitly documented.