Expand ~/ to home directory in config file paths #1933

Description

Paths in config files support the ~appFolder and ~dataFolder tokens, but ~/ isn't expanded to the user's home directory. In shells, git (core.excludesFile, include.path) and tools like mitmproxy, ~/ means home. Setting a path like ~/mocks/mocks.json makes Dev Proxy treat ~ as a literal folder name relative to the config file.

Evidence

DevProxy.Abstractions/Utils/ProxyUtils.cs:189-198 (ReplacePathTokens) replaces only ~dataFolder and ~appFolder. GetFullPath then resolves the result relative to the config file.

Expected

Expand a leading ~/ (and ~\ on Windows) to the user's home directory in all path options, alongside the existing tokens.