Mobile UI pass: sheet swipe, ice-scene layering, contrast, touch targets

Phones (<=639px) only for layout/gestures; the theme-level fixes apply
everywhere, as they are token/design changes.

Settings sheet
- Swipe-to-dismiss reusing the InstallSheet gesture: the sheet follows the
  finger, closes past ~90px or on a fast flick, snaps back otherwise. Drag
  starts only from the handle/header and only while the body is scrolled to
  the top. Backdrop tap still closes.
- Fixed header + scrollable body: pb-safe + spacer, so nothing is clipped;
  a scroll cue (chevron) fades in while more content is below and out at
  the end.
- Show/Save stack under the field at 44px on phones; close, Test connection
  and Remove key are 44px too. Remove key is now a rose destructive action
  with a confirmation that the full-screen key setup comes back.
- API key note split into a short privacy line plus a collapsible
  'Using the local daemon?' tip (OLLAMA_AUTH=local / .env.local / signin).
- Fixed the missing space in the English tip ('ollama signin instead.').
- Health: kept the auto-check and banner; added a loading row and a
  'Checked just now' / 'Checked at HH:MM' freshness label (also for errors).

Ice scene / readability
- Verified the orbs were never above content (fixed z-index:-1 layer,
  pointer-events:none); they were just shining through the glass. Phones get
  lower blob/orb opacity and orbs tucked to the edges; the bottom-right orb
  is moved out from under the tab bar and the tab bar paints a more opaque
  surface so its labels hold contrast.

Contrast / themes
- Dark --text-subtle raised to #9db1d0 (8.6:1 page, 7.2:1 glass); helper
  text now uses the tokens.
- Disabled buttons are a visible muted chip (.btn-disabled) instead of a
  40%-opacity ghost.
- One ice primary gradient in both themes; danger/success now actually show
  their colour (bg-none strips the primary background-image that used to
  paint over !bg-rose-600).
- Light mode: cool card rims instead of white-on-white, stronger shadow.

Redundancy / touch
- Removed only the header gear; the hamburger drawer (folders, Settings,
  theme) and the tab-bar Settings stay.
- Theme toggle is a bordered chip with an action aria-label (drawer row too).
- Empty library hides the folder pills, demotes Import to a quiet link and
  keeps a single primary CTA. 44px targets for nav rows, segmented control
  and folder pills on phones.
- Fixed a pre-existing 16px horizontal overflow (header -mx-4 vs a
  padding-less parent) and let info values wrap instead of truncating.

Verified: mobile suite 47/47 (EN+CS, 360/390px), pixel-sampled contrast
audit 0 runs below WCAG AA (8 runs, both themes/locales; axe marks the glass
'incomplete'), i18n 27/27, desktop regression 72/72, lint + build clean.
Service worker cache bumped to freezmo-v5.

components/AppHeader.tsx

@@ -3,7 +3,7 @@
 import Link from "next/link";
 import { useEffect, useState } from "react";
 
-import { GearIcon, MenuIcon } from "@/components/icons";
+import { MenuIcon } from "@/components/icons";
 import { SettingsDialog } from "@/components/SettingsDialog";
 import { ThemeToggle } from "@/components/ThemeToggle";
 import { useI18n } from "@/lib/i18n";
@@ -35,7 +35,10 @@ export function AppHeader({ className, compact = false }: { className?: string;
     <>
       <header
         className={cn(
-          "glass sticky top-0 z-40 -mx-4 mb-6 px-4 lg:hidden sm:-mx-6 sm:px-6",
+          // No negative margins here: the header is a direct child of <main>,
+          // which has no horizontal padding — the -mx-4 made it 16px wider
+          // than the viewport and caused a horizontal scroll on phones.
+          "glass sticky top-0 z-40 mb-6 px-4 lg:hidden sm:px-6",
           className,
         )}
       >
@@ -44,7 +47,7 @@ export function AppHeader({ className, compact = false }: { className?: string;
             type="button"
             onClick={() => sidebarOpen.toggle()}
             aria-label={t("header.openMenu")}
-            className="mr-1 grid size-9 shrink-0 place-items-center rounded-full text-[var(--text-muted)] transition hover:bg-[var(--hover)] hover:text-[var(--text)]"
+            className="mr-1 grid size-9 shrink-0 touch-target place-items-center rounded-full text-[var(--text-muted)] transition hover:bg-[var(--hover)] hover:text-[var(--text)]"
           >
             <MenuIcon className="size-5" />
           </button>
@@ -69,15 +72,8 @@ export function AppHeader({ className, compact = false }: { className?: string;
           </Link>
 
           <div className="flex items-center gap-1">
-            <button
-              type="button"
-              onClick={() => setSettingsOpen(true)}
-              aria-label={t("header.openSettings")}
-              title={t("common.settings")}
-              className="inline-flex size-9 items-center justify-center rounded-full text-[var(--text-muted)] transition hover:bg-[var(--hover)] hover:text-[var(--text)]"
-            >
-              <GearIcon className="size-[18px]" />
-            </button>
+            {/* Settings lives in the tab bar and the drawer; the old header
+                gear was the same control a third time. */}
             <ThemeToggle />
           </div>
         </div>