feat: add visual review workflow for automated PR screenshot comparison

Adds a label-triggered GitHub Actions workflow that automatically generates
before/after screenshots when web UI changes are made in a PR. Uses smart
dependency analysis to only screenshot pages affected by the changed files.

Key components:
- Reverse dependency analyzer: traces changed files through the import graph
  to find which +page.svelte routes are affected
- Screenshot scenarios: Playwright tests using existing mock-network infrastructure
  (no Docker/backend needed) for fast, deterministic screenshots
- Pixel comparison: generates diff images highlighting changed pixels
- GitHub Actions workflow: triggered by 'visual-review' label, posts results
  as a PR comment with change percentages per page

https://claude.ai/code/session_01XSTqDJXuR4jaLN7SGm3uES

.gitignore

@@ -24,6 +24,7 @@ open-api/typescript-sdk/build
 mobile/android/fastlane/report.xml
 mobile/ios/fastlane/report.xml
 
+screenshots-output
 vite.config.js.timestamp-*
 .pnpm-store
 .devcontainer/library