Add structured startup arguments builder

[Kosinkadink]

Replaces the plain text input for launch args with a structured editor.

Changes

• ArgsBuilder component: Renders a text input (source of truth) with a gear button that toggles a helper panel with structured controls for common CLI args
• Schema-driven: Args defined in args-schema.ts with types: boolean, number, string, select, optional-string. Supports version-aware filtering (since) and mutually-exclusive groups (exclusiveGroup)
• Bidirectional sync: Editing the text field updates helper controls; using controls updates the text field. Parsing tokenizes respecting quotes, separates known vs extra args
• 4 common args: --port (number), --listen (optional-string: checkbox + IP input), --front-end-version (select: Latest/Custom with text input), --enable-manager (boolean)
• Select with Custom option: Select-type args support a Custom option that reveals a text input for arbitrary values
• Field reorder: Settings tab fields reordered to: Startup Args, Launch Mode, Port Conflict, Use Shared Dirs, Browser Cache
• No data model changes: Raw args string remains the single source of truth in installations.json