perf: keep large-map navigation responsive and stable

[prayujt]

Summary

• batch generated terrain, structures, and remembered-fog sprites through a shared texture atlas
• update tile lookup and rendered tiles incrementally instead of rebuilding the visible scene for every streamed state change
• prune inactive tile containers after camera movement settles and skip hidden overlay animation work
• avoid no-op entity-store updates and cache minimap terrain during camera movement
• keep confirmed movement routes visible while stale, delayed, or route-less streamed order updates reconcile
• show move previews in blue, confirmed moves in green, and attacks in red before and after confirmation
• preserve the complete isometric map outline at low zoom
• group population trend, tax revenue, and food balance at the top of city management
• preserve existing terrain art, fog opacity, camera controls, interactions, calculations, and game rules

Verification

• npx prettier --check src/lib/components/MiniMap.svelte src/lib/game/sprites.ts src/routes/game/+layout.svelte src/routes/game/+page.svelte
• npx eslint src/lib/components/MiniMap.svelte src/lib/game/sprites.ts src/routes/game/+layout.svelte src/routes/game/+page.svelte
• npm run check
• npm run build

Note

The repository-wide npm run lint remains blocked by existing Prettier violations in 23 files outside this change; targeted formatting and ESLint checks pass for every changed file.