feat: UX improvements - voting UI, NFT sharing, mobile tx, offline support (#741 #734 #735 #740)

[Anuoluwapo25]

Summary

This branch addresses 4 UX improvement issues:

• ux: improve proposal voting UI with clear visual feedback #741 — Improve proposal voting UI with active vote state, percentage bar, deadline disabling, "already voted" message, voting power display, and animated count update
• ux: add 'Share on Twitter/X' button for earned NFT credentials #734 — Add 'Share on Twitter/X' and LinkedIn buttons for earned NFT credentials with pre-filled tweet text, credential URL, and analytics tracking
• ux: add mobile-optimized transaction confirmation UI #735 — Add mobile-optimized transaction confirmation UI with wallet detection (Lobstr vs Freighter), mobile signing instructions, QR code, and back-nav handling
• ux: add offline detection and graceful degradation #740 — Add offline detection and graceful degradation: persistent banner, cached read-only data, auto-retry on reconnect, disable write ops when offline

Test plan

• Voting UI highlights user's current vote (For/Against active state)
• Vote count and percentage bar display correctly
• Voting disabled after proposal deadline
• "You have already voted" message shown for repeat voters
• User's voting power shown before casting vote
• Vote count animates on submission
• Twitter/X share button on credential page with pre-filled tweet text and verification URL
• LinkedIn share button present and functional
• Share events tracked in analytics
• Mobile wallet (Lobstr) vs desktop (Freighter) correctly detected
• Mobile-specific signing instructions shown on mobile devices
• Offline banner appears when navigator.onLine is false
• Read-only pages show cached data while offline
• Write operations (submit, vote, deposit) disabled when offline
• Pending requests auto-retry on reconnect

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