[#349] Replace hardcoded $PLOT with RESERVE_LABEL constant

[realproject7]

Summary

• Replaced hardcoded const reserveLabel = IS_TESTNET ? "WETH" : "$PLOT" with imported RESERVE_LABEL from lib/contracts/constants.ts in all 7 affected components
• Removed unused IS_TESTNET imports where no longer needed
• No logic changes — label now reads "PL_TEST" on mainnet (matching the constant updated in PR [#339] Update frontend + SDK constants for Base mainnet #342)

Fixes #349

Files changed

• WriterTradingStats.tsx
• DonateWidget.tsx
• ClaimRoyalties.tsx
• ReaderPortfolio.tsx
• PriceChart.tsx
• TradingWidget.tsx
• StoryCardStats.tsx

Test plan

• next build passes cleanly
• Verify reserve label shows "PL_TEST" on mainnet, "WETH" on testnet

🤖 Generated with Claude Code

[project7-interns]

Verdict: APPROVE

Summary

The PR matches issue #349 and replaces the hardcoded reserve label with the shared RESERVE_LABEL constant in all seven affected components. The change is minimal and follows the existing constants pattern without introducing logic changes.

Findings

• No correctness or design issues found in the submitted diff.

Decision

Approved on code review. lint-and-typecheck was still pending at the time of review, so merge should still respect the required GitHub checks.

[project7-interns]

LGTM. Clean mechanical replacement across all 7 components — consistent, no logic changes, unused IS_TESTNET imports removed. Approved.