feat(contracts): Multi-signer e-signature system with PDF overlay

- Add multi-signer contract creation with staff/customer selection
- Add signer-specific signing URLs (/sign/s/{token})
- Add sequential and parallel signing modes
- Fix can_sign check in frontend (use top-level response field)
- Fix required field validation to work for all template types
- Fix PDF overlay generation for HTML templates with generated PDFs
- Add signature pre-fill support in template field editor
- Add signature remember/re-apply feature during signing
- Update PDFOverlayService to read from contract.original_pdf_path

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

frontend/QUICK_TEST_GUIDE.md

@@ -0,0 +1,117 @@
+# Quick Test Guide - useTenantExists Hook
+
+## Setup (One-time)
+
+```bash
+cd /home/poduck/Desktop/smoothschedule2/frontend
+./install-test-deps.sh
+```
+
+Then add to `package.json`:
+```json
+{
+  "scripts": {
+    "test": "vitest",
+    "test:ui": "vitest --ui",
+    "test:run": "vitest run",
+    "test:coverage": "vitest run --coverage"
+  }
+}
+```
+
+## Run Tests
+
+```bash
+# Run all tests (watch mode)
+npm run test
+
+# Run once (CI mode)
+npm run test:run
+
+# Run with UI
+npm run test:ui
+
+# Run with coverage
+npm run test:coverage
+
+# Run only useTenantExists tests
+npm run test -- useTenantExists
+
+# Run specific test by name
+npm run test -- -t "returns exists: true"
+```
+
+## Files Created
+
+| File | Location | Purpose |
+|------|----------|---------|
+| **Test Suite** | `src/hooks/__tests__/useTenantExists.test.ts` | 19 comprehensive tests |
+| **Vitest Config** | `vitest.config.ts` | Test runner configuration |
+| **Test Setup** | `src/test/setup.ts` | Global test setup |
+| **Install Script** | `install-test-deps.sh` | Dependency installation |
+
+## Test Coverage
+
+✓ **All Required Tests Implemented:**
+
+1. Returns exists: true when API returns 200
+2. Returns exists: false when API returns 404
+3. Returns exists: false when subdomain is null
+4. Returns exists: false on other API errors
+5. Shows loading state while fetching
+6. Caches results (5 minute staleTime)
+7. Does not make API call when subdomain is null
+
+Plus **12 additional tests** for edge cases and error handling.
+
+## Expected Output
+
+```
+✓ src/hooks/__tests__/useTenantExists.test.ts (19)
+  ✓ useTenantExists
+    ✓ API Success Cases (2)
+    ✓ API Error Cases (4)
+    ✓ Null Subdomain Cases (3)
+    ✓ Loading States (2)
+    ✓ Caching Behavior (2)
+    ✓ Query Key Behavior (1)
+    ✓ Edge Cases (3)
+    ✓ Query Retry Behavior (2)
+
+Test Files  1 passed (1)
+Tests  19 passed (19)
+```
+
+## Troubleshooting
+
+| Issue | Solution |
+|-------|----------|
+| `Cannot find module 'vitest'` | Run `./install-test-deps.sh` |
+| `beforeAll is not defined` | Check `vitest.config.ts` has `globals: true` |
+| `document is not defined` | Ensure `environment: 'jsdom'` in config |
+| Tests timeout | Increase `testTimeout` in config |
+
+## Documentation
+
+- **TEST_SUMMARY.md** - Complete test suite documentation
+- **SETUP_TESTING.md** - Detailed setup instructions
+- **TESTING.md** - Comprehensive testing guide
+- **src/hooks/__tests__/README.md** - Hook testing patterns
+
+## Next Steps
+
+1. ✓ Test files created
+2. → Install dependencies: `./install-test-deps.sh`
+3. → Update package.json scripts
+4. → Run tests: `npm run test`
+5. → Check coverage: `npm run test:coverage`
+
+---
+
+**Quick Start:**
+```bash
+cd /home/poduck/Desktop/smoothschedule2/frontend
+./install-test-deps.sh
+# Add scripts to package.json
+npm run test
+```