Stellar Expert deep-link helper everywhere

[truthixify]

Tier: S (½-1 day) Type: feature

Context

good-first-issue

Scope

Today some places link to stellar.expert (txs from Send success) and others don't (stealth addresses on Receive, contract events). Add a centralized helper and surface links consistently.

Acceptance criteria

• Centralize URL generation in src/lib/explorer.ts (already exists, extend)
• Helpers: accountUrl, txUrl, contractUrl, assetUrl, operationUrl
• Audit Receive, Send, Activity for missing links
• Add "View on stellar.expert" links wherever a Stellar identifier appears
• Network-aware (testnet vs public)

Files to start with

• Helpers complete
• Audit findings addressed
• Consistent labelling ("View on stellar.expert")
• a11y: rel="noopener"

Why this matters

• src/lib/explorer.ts
• All Stellar components