fix: resolve all sonarjs/no-duplicate-string lint warnings

[Copilot]

Eliminates all 11 sonarjs/no-duplicate-string warnings surfaced by npm run lint by extracting repeated string literals into named constants and consolidating duplicate API key guard logic.

📝 Summary

11 sonarjs/no-duplicate-string warnings across 6 files — each caused by string literals repeated 3–8 times. Fixed by extracting constants and removing redundant inline guards in favour of the existing ensureApiKey() helper.

🔧 Changes

• criteriaScoring.js — BULLET_PREFIX_THE_SYSTEM / BULLET_PREFIX_SYSTEM_MUST constants replace 3× inline literals each
• llmService.js — improveStoryWithAI and improveCriteriaWithAI now delegate to the existing ensureApiKey() helper instead of duplicating the guard; NOT_PROVIDED constant replaces 3× inline '(not provided)' in buildCriteriaPrompt
• CriteriaScoreBreakdown.jsx — module-level COLOR_GREEN constant replaces 3× 'text-green-600'
• criteriaScoring.test.js — BULLET_CRITERIA constant replaces 3 identical inline arrays
• llmService.test.js — TEST_API_KEY (8 uses) and SAMPLE_CRITERION (4 uses) constants extracted
• scoreSoThatStatement.test.js — GRADE_NEEDS_WORK constant replaces 3× 'Needs work'

Notable: the llmService.js fix also removes dead duplicate validation code — ensureApiKey() already existed at module scope and is a function declaration (hoisted), so replacing the inline guards is a pure deduplification with no behaviour change.

🎯 Motivation

npm run lint reported 11 warnings. Reducing string duplication improves maintainability: rename/update in one place rather than hunting literals.

🧪 Testing

• npm run lint — 0 warnings (was 11)
• npm test -- --run — 222/222 tests pass

📸 Screenshots (optional)

N/A

✅ Checklist

• Code compiles and runs
• Tests added or updated (if applicable)
• Documentation updated (if needed)
• No linting or formatting issues
• PR title is clear and descriptive

[Copilot]

Pull request overview

Refactors the codebase to eliminate 11 sonarjs/no-duplicate-string lint warnings by extracting repeated string literals into named constants and removing duplicated API key guard code in favor of an existing ensureApiKey() helper.

Changes:

• Extract repeated literals (bullet prefixes, color classes, test fixtures, grade labels) into named constants across 6 files.
• Replace duplicated inline API key validation with ensureApiKey() helper in improveStoryWithAI / improveCriteriaWithAI.
• No behavior change; refactor-only.

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
src/criteriaScoring.js	Extracts BULLET_PREFIX_THE_SYSTEM / BULLET_PREFIX_SYSTEM_MUST constants.
src/llmService.js	Delegates to ensureApiKey(); adds NOT_PROVIDED constant.
src/components/CriteriaScoreBreakdown.jsx	Adds COLOR_GREEN constant for repeated Tailwind class.
src/test/criteriaScoring.test.js	Adds shared BULLET_CRITERIA fixture.
src/test/llmService.test.js	Adds TEST_API_KEY and SAMPLE_CRITERION constants.
src/test/scoreSoThatStatement.test.js	Adds GRADE_NEEDS_WORK constant.