feat: unique color picker for class types in schedule editor

- Add clickable color picker in schedule legend (16 distinct colors)
- Two-pass smart assignment: explicit colors first, then unused palette slots
- Hide already-used colors from the picker (both explicit and fallback)
- Colors saved to classes section and flow to public site schedule dots
- Expanded palette: rose, orange, amber, yellow, lime, emerald, teal, cyan,
  sky, blue, indigo, violet, purple, fuchsia, pink, red

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/components/sections/schedule/DayCard.tsx

@@ -1,8 +1,7 @@
 import { Clock, User } from "lucide-react";
 import type { ScheduleDay } from "@/types/content";
-import { TYPE_DOT } from "./constants";
 
-export function DayCard({ day }: { day: ScheduleDay }) {
+export function DayCard({ day, typeDots }: { day: ScheduleDay; typeDots: Record<string, string> }) {
   return (
     <div className="rounded-2xl border border-neutral-200 bg-white dark:border-white/[0.06] dark:bg-[#0a0a0a] overflow-hidden">
       {/* Day header */}
@@ -43,7 +42,7 @@ export function DayCard({ day }: { day: ScheduleDay }) {
             </div>
             <div className="mt-2 flex items-center gap-2 flex-wrap">
               <div className="flex items-center gap-2">
-                <span className={`h-2 w-2 shrink-0 rounded-full ${TYPE_DOT[cls.type] ?? "bg-white/30"}`} />
+                <span className={`h-2 w-2 shrink-0 rounded-full ${typeDots[cls.type] ?? "bg-white/30"}`} />
                 <span className="text-xs text-neutral-500 dark:text-white/40">{cls.type}</span>
               </div>
               {cls.level && (