Align WinForms frontend to reference layout (left rail, top bar, compact cards)

[Copilot]

This PR reworks the frontend structure to match the provided concept image instead of only recoloring the existing UI. It shifts the Game Manager toward the intended composition: left navigation rail, top action bar, compact launcher rows, and image-first game cards.

• Shell layout restructured (reference-driven)

  • Replaced the simple top-toolbar shell with a 2-column root layout: fixed left sidebar + main content area.
  • Added vertical sidebar icon actions with active-state styling.
  • Promoted the top bar to a dedicated action/status strip above tab content.

• Tab and content framing adjusted

  • Updated tab sizing/spacing to better match the visual proportions in the mockup.
  • Tuned paddings/margins so sections align with the new rail + header geometry.

• Game Manager hero and section composition updated

  • Refactored hero panel into icon + text composition (Game Library, summary, subtitle).
  • Preserved existing dynamic summary binding while shifting presentation to the target style.
  • Kept launcher and installed-games sections as separate blocks with revised spacing hierarchy.

• Launcher cards redesigned for compact horizontal density

  • Added icon/avatar-style leading block and tightened text width.
  • Kept launcher title/path semantics, but reshaped cards to fit multi-column rows similar to the reference.

• Game cards simplified to image-first layout

  • Removed verbose metadata stack from cards in favor of large artwork + compact footer row.
  • Footer now uses install-status badge plus a right-side menu/action affordance.
  • Existing interaction remains intact (openGameDirectory still wired through card action).

• Theme tokens expanded for layout parity

  • Added sidebar-specific and gradient-ready color tokens in shared UI helpers.
  • Continued centralizing style values in UIHelpers to keep component theming consistent.

var root = new TableLayoutPanel { Dock = DockStyle.Fill, ColumnCount = 2 };
root.ColumnStyles.Add(new ColumnStyle(SizeType.Absolute, 72));       // left rail
root.ColumnStyles.Add(new ColumnStyle(SizeType.Percent, 100));       // main content

var shell = new TableLayoutPanel { Dock = DockStyle.Fill, RowCount = 2 };
shell.RowStyles.Add(new RowStyle(SizeType.Absolute, 86));            // top action bar
shell.RowStyles.Add(new RowStyle(SizeType.Percent, 100));            // tabs/content