fix(landing): design audit fixes — hamburger menu, dead links, branding, spacing (#117)

* fix(landing): design audit fixes — hamburger menu, dead links, branding, spacing

- Add mobile hamburger menu with animated open/close and click-outside dismiss
- Create Privacy and Terms pages (footer links were dead # anchors)
- Change "Decision Tree Platform" to "AI-Powered Troubleshooting for MSPs" on login, register, and HTML title
- Fix register page icon color (was red/coral via CSS invert, now uses BrandLogo directly)
- Replace "0 Ticket Notes Written by Hand" stat with "100% Auto-Generated Documentation"
- Increase nav link touch targets to 44px minimum
- Fix heading hierarchy: section titles are now <h2>, standardize H3 to 1.25rem
- Tighten section spacing (6rem → 4rem padding, remove extra 5rem spacer)
- Add color-scheme: dark to HTML element
- Replace all transition: all with specific properties (10 occurrences)
- Fix loading ellipsis (... → …)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

* fix(mobile): responsive modals + landing preview overflow

- PrepareSessionModal: bottom-sheet on mobile, centered on desktop
- IntakeFormModal: bottom-sheet on mobile, responsive padding
- ShareTreeModal: bottom-sheet on mobile, full-width on small screens
- Landing preview: hide URL bar and window controls on mobile (<900px)
  to prevent 189px horizontal overflow

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

* fix(mobile): collapse search bar to icon on mobile

On mobile (<640px), the full search bar with placeholder text and ⌘K
badge was taking too much space in the topbar. Now shows just a
magnifying glass icon that opens the same command palette on tap.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

---------

Co-authored-by: chihlasm <michael@resolutionflow.com>
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

frontend/src/pages/LoginPage.tsx

@@ -79,7 +79,7 @@ export function LoginPage() {
             <span>Resolution</span><span className="text-gradient-brand">Flow</span>
           </h1>
           <p className="mt-2 text-base font-medium text-muted-foreground sm:mt-3 sm:text-lg">
-            Decision Tree Platform
+            AI-Powered Troubleshooting for MSPs
           </p>
           <p className="mt-1 text-sm text-muted-foreground/70 sm:mt-2">
             Sign in to your account