Add modal settings page to control brightness, visibility, and which buttons appear in the control window

[garrettcampbell3]

Add Settings Window

Adds a new Settings window accessible via a gear button (⚙️) on the control bar. The settings window opens as a modal dialog and provides fine-grained controls that go beyond the toolbar buttons.

New Settings Window Features

• Brightness — slider (20%–100%) for precise adjustment
• Color Temperature — slider (cool ↔ warm) with visual labels
• Exclude from Screen Capture — toggle to hide edge light from screenshots/Teams
• Control Bar Buttons — choose which buttons appear in the floating control bar: - Brightness buttons
• Color temperature buttons
• Window control buttons (toggle, switch monitor, all monitors)

Changes

• SettingsWindow.xaml / .xaml.cs — new resizable settings window with card-based Fluent UI
• AppSettings.cs — added ShowBrightnessButtons, ShowColorTempButtons, ShowWindowControlButtons persisted settings
• ControlWindow.xaml / .xaml.cs — gear button wired up; button visibility updates immediately when settings change
• MainWindow.xaml.cs — added SetBrightness(), GetBrightness(), GetColorTemperature(), GetSettings() public APIs; refactored brightness methods to use SetBrightness

Screenshots

Control Window with various settings disabled/enabled

Without brightness

Without warmth

Without monitor control

Without any

[shanselman]

Thanks for this, Garrett — the settings window is a useful direction, and I like the idea of making brightness/color/exclude/buttons discoverable instead of only toolbar/hotkey driven.

I took a deep pass over this alongside the persistence work and I don't want to merge it as-is yet. Could you please rebase after the current settings-persistence changes land and tighten up the following items?

Required before merge

1. Hide the toggle button when window controls are disabled

   The setting text says the window control group covers toggle/switch/all-monitor buttons, and the XAML names ToggleLightButton, but ApplyButtonVisibility() only hides SwitchMonitorButton and AllMonitorsButton.

   Suggested fix:

   ToggleLightButton.Visibility = windowCtrlVis;
   SwitchMonitorButton.Visibility = windowCtrlVis;
   AllMonitorsButton.Visibility = windowCtrlVis;

2. Rebase onto the persistence implementation and use one persisted path for sliders

   Brightness/color/on-off state now persist, with clamping for bad settings values. After rebasing, make sure the settings sliders call the same persistence-aware methods used by hotkeys/buttons. In particular:

   • brightness slider changes should update the live UI and save the clamped value
   • color-temperature slider changes should update the live UI, all monitor windows, and save the clamped value
   • no path should write raw NaN, Infinity, or out-of-range values into settings

3. Avoid exposing the mutable AppSettings object directly if possible

   GetSettings() => settings works, but it couples the settings dialog to the whole settings object. Prefer narrow APIs on MainWindow, for example:

   public bool ShowBrightnessButtons => settings.ShowBrightnessButtons;
   public void SetShowBrightnessButtons(bool value) { ... save ... }

   Same idea for color-temp buttons and window-control buttons. That keeps persistence, validation, and future side effects centralized.

4. Clean up unrelated diff noise

   There is an accidental indentation change in MoveToNextMonitor() around double newLeft = .... Please revert that hunk so this PR stays focused on the settings UI.

5. Fix the small settings copy typo

   Show monitor conrol buttons -> Show monitor control buttons.

Manual validation I would like before merge

Please include a short test note covering:

• Release build succeeds on Windows.
• Gear button opens the settings dialog modally and returns focus correctly when closed.
• Brightness slider changes the light live and survives app restart.
• Color-temperature slider changes the main window and all-monitor windows live, and survives app restart.
• Exclude-from-capture checkbox stays in sync with the tray menu item.
• Each control-bar button group can be hidden/shown, including the toggle button.
• The settings gear and exit button remain reachable even if all optional groups are hidden.
• Light/dark/system theme and high-DPI layout look reasonable.
• Multi-monitor mode still works after changing brightness/color from the settings dialog.

This is close, but because it touches user-visible WPF behavior and overlaps with persisted settings, I want it rebased and manually smoke-tested rather than merging the current branch directly.

[garrettcampbell3]

Please include a short test note covering:

Release build succeeds on Windows.
Gear button opens the settings dialog modally and returns focus correctly when closed.
Brightness slider changes the light live and survives app restart.
Color-temperature slider changes the main window and all-monitor windows live, and survives app restart.
Exclude-from-capture checkbox stays in sync with the tray menu item.
Each control-bar button group can be hidden/shown, including the toggle button.
The settings gear and exit button remain reachable even if all optional groups are hidden.
Light/dark/system theme and high-DPI layout look reasonable.
Multi-monitor mode still works after changing brightness/color from the settings dialog.

@shanselman I've updated and confirmed the manual validation before merge for all of the smoke testing on the local build. I have confirmed all of the above, except for the release build as I don't want to push a tag to kick off a release from a topic branch)

Thanks! Happy to make more changes and test more things as needed/requested.