Standardize fetch retry action copy on landing page

[edehvictor]

Closes #184

Closes #182

Changes

• standardized fetch retry action button text to a single label: Try again
• moved landing fetch retry helper copy to shared constants/functions in LandingPage for consistent tone
• kept retry logic unchanged (copy-only update)

Testing

• not run in this shell environment (tooling setup constraints); change is copy-only and scoped to LandingPage

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