HIGH: Add HTMX Loading States and Visual Feedback Across All Modes

[nathanbangwa243]

Issue

HTMX swaps lack visual feedback during requests. No loading indicator, spinner, or animation cues users that an action is processing.

Current State

• Bingo board squares toggle colors but with no loading state
• Card Deck draw requests have no visual indication of processing
• Scavenger Hunt marks update without confirmation feedback
• No toast notifications for achievements

Impact

• Users uncertain if interaction registered
• Perceived latency feels worse than actual latency
• No celebration/confirmation on win state (scavenger hunt)
• Poor feedback loop for accessibility

Recommended Implementation

• Add HTMX hx-indicator spinners during requests
• Implement micro-animations for state transitions (scale, fade, progress)
• Add toast notification on Bingo victory
• Provide visual confirmation on Card Deck draw (brief glow/highlight)
• Disable buttons during processing to prevent double-clicks

Files to Update

• app/templates/base.html (add spinner template, toast container)
• app/static/css/app.css (loading animation keyframes)
• app/templates/components/game_screen.html (add indicator to toggle buttons)
• app/templates/components/scavenger_list.html (add indicator to mark buttons)
• app/templates/components/card_deck.html (add indicator to draw button)