feat(ui): add status bar blame and logging infrastructure

[CalvinAllen]

Summary

• Add real-time blame display in Visual Studio status bar (closes feat(ui): add status bar blame indicator #19)
• Add configurable output pane logging with log levels (closes feat(logging): implement logging levels for output pane #66)
• Refactor services to use proper MEF patterns with interface-backed exports
• Upgrade LibGit2Sharp to 0.31.0 and disable owner validation

Features

Status Bar Blame (#19)

• Shows blame info for current line in status bar
• Configurable format template: {author}, {date}, {message}, {sha}
• Options for relative dates and max display length
• Updates in real-time as cursor moves

Logging Infrastructure (#66)

• New OutputPaneService writes to "Git Ranger" output pane
• Configurable log levels: None, Error, Info, Verbose
• Default level is Error for minimal noise
• Setting in Tools > Options > Git Ranger > General > Diagnostics

MEF Refactoring

• All services now interface-backed with [Export(typeof(IService))]
• Proper constructor injection with [ImportingConstructor]
• Factories pass services to non-MEF components via constructor

LibGit2Sharp Upgrade

• Upgraded from 0.30.0 to 0.31.0
• Added GlobalSettings.SetOwnerValidation(false) to fix "not owned by current user" errors
• Users no longer need to configure safe.directory manually

Test Plan

• Open file in Git repo - status bar shows blame for current line
• Move cursor between lines - status bar updates
• Disable status bar blame in options - status bar clears
• Change log level in options - output pane respects setting
• Inline blame and gutter margin still working