test(P14.1): add comprehensive backend API test suite

Add 134 tests as independent test project:
- test_auth.py (5): Login, JWT, protected endpoints
- test_users.py (8): User CRUD, permissions
- test_projects.py (8): Project CRUD, ownership
- test_milestones.py (7): Milestone CRUD, filtering
- test_tasks.py (8): Task CRUD, filtering
- test_comments.py (5): Comment CRUD, permissions
- test_roles.py (9): Role/permission management
- test_milestone_actions.py (17): Milestone state machine
- test_task_transitions.py (34): Task state machine
- test_propose.py (19): Propose CRUD, lifecycle
- test_misc.py (14): Notifications, activity, API keys, dashboard

Setup:
- conftest.py: SQLite in-memory DB, fixtures
- requirements.txt: Dependencies
- pyproject.toml: Pytest config
- README.md: Documentation

README.md

@@ -1 +1,52 @@
 # HarborForge.Backend.Test
+
+Independent test suite for HarborForge.Backend.
+
+## Setup
+
+```bash
+# Create virtual environment
+python3 -m venv venv
+source venv/bin/activate
+
+# Install dependencies
+pip install -r requirements.txt
+```
+
+## Run Tests
+
+```bash
+# Run all tests
+pytest
+
+# Run specific test file
+pytest tests/test_auth.py
+
+# Run with verbose output
+pytest -v
+
+# Run with coverage (requires pytest-cov)
+pytest --cov=../HarborForge.Backend/app --cov-report=html
+```
+
+## Test Structure
+
+| File | Tests | Coverage |
+|------|-------|----------|
+| `test_auth.py` | 5 | Login, JWT, protected endpoints |
+| `test_users.py` | 8 | User CRUD, permissions |
+| `test_projects.py` | 8 | Project CRUD, ownership |
+| `test_milestones.py` | 7 | Milestone CRUD, filtering |
+| `test_tasks.py` | 8 | Task CRUD, filtering |
+| `test_comments.py` | 5 | Comment CRUD, permissions |
+| `test_roles.py` | 9 | Role/permission management |
+| `test_milestone_actions.py` | 17 | Milestone state machine actions |
+| `test_task_transitions.py` | 34 | Task state machine transitions |
+| `test_propose.py` | 19 | Propose CRUD, accept/reject/reopen |
+| `test_misc.py` | 14 | Notifications, activity log, API keys, dashboard |
+
+**Total: 134 tests**
+
+## How It Works
+
+Tests import the backend code from `../HarborForge.Backend/` via path manipulation in `conftest.py`. Uses SQLite in-memory database for fast, isolated tests.