chore: refactor hardcoded values to constants (v0.5.1)

Major internal refactoring to eliminate hardcoded values and improve
maintainability. Guardian now fully passes its own quality checks!

Changes:
- Extract all RepositoryViolation messages to domain constants
- Extract all framework leak template strings to centralized constants
- Extract all layer paths to infrastructure constants
- Extract all regex patterns to IMPORT_PATTERNS constant
- Add 30+ new constants for better maintainability

New files:
- src/infrastructure/constants/paths.ts (layer paths, patterns)
- src/domain/constants/Messages.ts (25+ repository messages)
- src/domain/constants/FrameworkCategories.ts (framework categories)
- src/shared/constants/layers.ts (layer names)

Impact:
- Reduced hardcoded values from 37 to 1 (97% improvement)
- Guardian passes its own src/ directory checks with 0 violations
- All 292 tests still passing (100% pass rate)
- No breaking changes - fully backwards compatible

Test results:
- 292 tests passing (100% pass rate)
- 96.77% statement coverage
- 83.82% branch coverage

packages/guardian/package.json

@@ -1,6 +1,6 @@
 {
     "name": "@samiyev/guardian",
-    "version": "0.5.0",
+    "version": "0.5.1",
     "description": "Code quality guardian for vibe coders and enterprise teams - catch hardcodes, architecture violations, and circular deps. Enforce Clean Architecture at scale. Works with Claude, GPT, Copilot.",
     "keywords": [
         "puaros",