Fix the mode-choice redundancy: standardized names, deep links, compact switch

Terminology (lib/i18n-dict.ts)
- One name per mode everywhere: "Study Deck" / "Studijní balíček" and
  "Homework Solver" / "Řešitel úkolů". The library empty-state cards and the
  /create switcher now read the same, so the choice no longer changes name
  between screens.

Deep links
- Library quick actions carry the mode: /create?mode=deck and
  /homework?mode=homework.
- Both pages canonicalize: /create?mode=homework redirects to the homework
  flow and /homework?mode=deck redirects to /create, so a mode link always
  opens that mode directly.

/create
- The two bulky square cards (106px tall, wrapping/clipping "Study Deck &
  Qu…" on phones) are replaced by a compact segmented control (52px) placed
  directly above "1. Add your notes": ice pill, snowflake/sparkles icons,
  44px segments and one-line labels at 360px. The pill slides to the chosen
  segment and the route follows ~190ms later, so toggling reads as one smooth
  transition (immediate under prefers-reduced-motion).

Service worker: freezmo-v9.

Verified: mode-switch suite 26/26 (deep links, cross-mode redirects, 52px
control, 44px segments, no clipping/wrapping at 360px, "1. Add your notes" at
y=394 of 740 with the upload controls above the fold, pill slide, axe contrast,
en+cs, phone+desktop), mobile 49/49, i18n 27/27, desktop regression 73/73.
Lint + build clean.

components/LibraryScreen.tsx

@@ -228,7 +228,7 @@ export function LibraryScreen() {
                assignment. Stacked on phones, side by side from 640px up. */
             <div className="grid w-[min(24rem,calc(100vw_-_3rem))] gap-3 sm:w-[36rem] sm:grid-cols-2">
               <Link
-                href="/create"
+                href="/create?mode=deck"
                 className="card card-hover touch-target flex items-center gap-3 border-accent-400/60 p-3.5 text-left sm:p-4"
               >
                 <span
@@ -242,7 +242,7 @@ export function LibraryScreen() {
                 </span>
               </Link>
               <Link
-                href="/homework"
+                href="/homework?mode=homework"
                 className="card card-hover touch-target flex items-center gap-3 p-3.5 text-left sm:p-4"
               >
                 <span