Improve run creation workflow with filters, local box art, and sticky nav

Use local /boxart/{slug}.png images instead of database boxArtUrl with
color-swatch fallback. Add region filter pills and run-status checkboxes
(hide active/completed) to GameGrid. Move the Next button into a sticky
top bar showing selected game summary so it's always visible. Capitalize
region names in all display locations.

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

frontend/src/components/GameCard.tsx

@@ -1,3 +1,4 @@
+import { useState } from 'react'
 import type { Game } from '../types'
 
 const DEFAULT_COLOR = '#6366f1' // indigo-500
@@ -10,6 +11,8 @@ interface GameCardProps {
 
 export function GameCard({ game, selected, onSelect }: GameCardProps) {
   const backgroundColor = game.color ?? DEFAULT_COLOR
+  const [imgError, setImgError] = useState(false)
+  const boxArtSrc = `/boxart/${game.slug}.png`
 
   return (
     <button
@@ -19,11 +22,12 @@ export function GameCard({ game, selected, onSelect }: GameCardProps) {
         selected ? 'ring-2 ring-blue-500 scale-105 shadow-lg' : 'shadow'
       }`}
     >
-      {game.boxArtUrl ? (
+      {!imgError ? (
         <img
-          src={game.boxArtUrl}
+          src={boxArtSrc}
           alt={game.name}
           className="w-full h-48 object-cover"
+          onError={() => setImgError(true)}
         />
       ) : (
         <div
@@ -41,7 +45,7 @@ export function GameCard({ game, selected, onSelect }: GameCardProps) {
         </h3>
         <div className="flex items-center gap-2 mt-1">
           <span className="text-xs px-2 py-0.5 rounded-full bg-gray-100 dark:bg-gray-700 text-gray-600 dark:text-gray-400">
-            {game.region}
+            {game.region.charAt(0).toUpperCase() + game.region.slice(1)}
           </span>
           {game.releaseYear && (
             <span className="text-xs text-gray-500 dark:text-gray-400">