Fix Windows crash saving tool definitions to a read-only install dir

[stytim]

Problem

On Windows, clicking Add Tool Definition crashed the app:

No RealSense devices found.
Added Tool1 with 4 spheres
An error occurred: create_directories: Access is denied.: ".\Tools"

The reporter hit this with no camera attached, but the save path is device-independent.

Root cause

GetDataDirectory() returned "." on Windows, so tool definitions (and CSV recordings) were written relative to the process working directory. For an app installed under C:\Program Files\… that directory is read-only, so fs::create_directories(".\Tools") failed with Access is denied. Because SaveToolDefinition() used the throwing create_directories overload, the filesystem_error propagated up to main() and terminated the app.

This is the same class of bug already fixed for macOS (where the .app working directory is /); Windows/Linux had been left on ".".

Fix

• GetDataDirectory() now returns %LOCALAPPDATA%\IR Tracking App on Windows — a writable per-user location — mirroring the macOS ~/Library/Application Support handling. Uses _wdupenv_s (not getenv) to stay warning-clean under /W4 and to preserve non-ASCII user names. Refactored to a single create/log/return path. Linux still falls back to ".".
• SaveToolDefinition() now uses the non-throwing create_directories(dir, ec) overload (and drops the throwing fs::exists): on failure it logs and skips persistence instead of crashing. The tool remains active for the session even if it can't be saved to disk.

Testing

• macOS: incremental build clean, no new warnings.
• Windows: the _WIN32 branch is compiled by this PR's build.yml / windows-2022 job (it couldn't be compiled on the macOS dev machine).

Notes

• Data location moves on Windows from the (broken, read-only) install dir to %LOCALAPPDATA%. No migration needed — the old location never worked for installed users, so there's nothing to lose.
• Two same-class but now-unreachable throwing filesystem sites remain (LoadToolDefinition, and the fs::exists loop in WriteToCSV on csvThread). Left out to keep this hotfix focused; happy to harden them in a follow-up.

Targets a v1.3.1 patch release over v1.3.0.