[V3] Add universal link support for macOS

[APshenkin]

Description

This PR backports https://github.com/wailsapp/wails/pull/4693/files to V3

Fixes # (issue)

Type of change

Please select the option that is relevant.

• [ ] Bug fix (non-breaking change which fixes an issue)
• [x] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)
• [ ] This change requires a documentation update

How Has This Been Tested?

Please describe the tests that you ran to verify your changes. Provide instructions so we can reproduce. Please also list any relevant details for your test configuration using wails doctor.

• [ ] Windows
• [x] macOS
• [ ] Linux

If you checked Linux, please specify the distro and version.

Test Configuration

# System

┌──────────────────────────────────────────────────┐
| Name          | MacOS                            |
| Version       | 26.1                             |
| ID            | 25B78                            |
| Branding      | MacOS 26.1                       |
| Platform      | darwin                           |
| Architecture  | arm64                            |
| Apple Silicon | true                             |
| CPU           | Apple M4 Max                     |
| CPU 1         | Apple M4 Max                     |
| CPU 2         | Apple M4 Max                     |
| GPU           | 40 cores, Metal Support: Metal 4 |
| Memory        | 128 GB                           |
└──────────────────────────────────────────────────┘

# Build Environment

┌─────────────────────────────────────────────────────────┐
| Wails CLI    | v3.0.0-dev                               |
| Go Version   | go1.24.0                                 |
| Revision     | 4a445ce218b58db4a16ee8fa84eac0d7c9a69932 |
| Modified     | false                                    |
| -buildmode   | exe                                      |
| -compiler    | gc                                       |
| CGO_CFLAGS   |                                          |
| CGO_CPPFLAGS |                                          |
| CGO_CXXFLAGS |                                          |
| CGO_ENABLED  | 1                                        |
| CGO_LDFLAGS  |                                          |
| GOARCH       | arm64                                    |
| GOARM64      | v8.0                                     |
| GOOS         | darwin                                   |
| vcs          | git                                      |
| vcs.modified | false                                    |
| vcs.revision | 4a445ce218b58db4a16ee8fa84eac0d7c9a69932 |
| vcs.time     | 2025-08-04T22:42:25Z                     |
└─────────────────────────────────────────────────────────┘

# Dependencies

┌────────────────────────────────────────────────────────────────────────┐
| Xcode cli tools | 2416                                                 |
| npm             | 10.9.2                                               |
| *NSIS           | Not Installed. Install with `brew install makensis`. |
|                                                                        |
└─────────────────────── * - Optional Dependency ────────────────────────┘

Please paste the output of wails doctor. If you are unable to run this command, please describe your environment in as much detail as possible.

Checklist:

• [ ] I have updated website/src/pages/changelog.mdx with details of this PR
• [x] My code follows the general coding style of this project
• [x] I have performed a self-review of my own code
• [x] I have commented my code, particularly in hard-to-understand areas
• [ ] I have made corresponding changes to the documentation
• [x] My changes generate no new warnings
• [ ] I have added tests that prove my fix is effective or that my feature works
• [x] New and existing unit tests pass locally with my changes

Summary by CodeRabbit

• New Features

  • Added Universal Link / web URL continuation on macOS so apps can open directly from supported web links.

• Refactor

  • Unified macOS URL handling and Apple Event processing, preserving existing window-reopen behavior.

• Documentation

  • Added cross-platform guidance for Universal Links and Web-to-App linking with configuration and hosting examples for macOS and Windows.

_{✏️ Tip: You can customize this high-level summary in your review settings.}