Detect Star Citizen installs on any drive and in custom library folders

[ckuma]

Problem

get_default_paths() only scanned drives C-F for the fixed layout …\Roberts Space Industries\StarCitizen. An install on another drive, or in a custom library folder, was never found — the app showed "No installations found" and the user had to browse manually.

Example that failed: G:\Games\StarCitizen\LIVE (drive G isn''t scanned, and Games\StarCitizen isn''t the expected folder name).

Changes

• Scan every fixed drive, not just C-F.
• Cover common custom roots: Games\Roberts Space Industries\StarCitizen, Games\StarCitizen, bare StarCitizen, in addition to the existing two.
• Read the authoritative path from the RSI Launcher log (%APPDATA%\rsilauncher\logs\log.log), which records the real library folder the user chose, e.g. … Installing Star Citizen LIVE … at G:\Games\StarCitizen. This is the only reliable way to find a fully custom library folder. (The launcher''s own settings store is encrypted, and the path is not in the registry, so the log is the practical source.)
• Every candidate is still verified against …\<ENV>\logbackups on disk before being offered, so stale log entries (old/moved installs) are dropped automatically.

Verification

On a machine with the game at G:\Games\StarCitizen\LIVE (drives C/F/G), get_default_paths() now returns:

{ "LIVE (G:)": "G:\\Games\\StarCitizen\\LIVE\\logbackups" }

The stale C:\Program Files\… entry parsed from the log is correctly discarded (folder no longer exists). ruff check and pyright both pass.

Notes

• Windows-only enhancement; Linux/macOS detection is unchanged.
• The equivalent C# app still uses the old C-F logic — happy to port this there in a follow-up if wanted.