feat: implement Phase 3 participant self-management (stories 4.5, 6.1)

Implemented features:
- Story 4.5: View Participant List - participants can see other active participants
- Story 6.1: Update Profile - participants can edit name and gift ideas before matching
- Utility functions for state management and business logic
- Comprehensive unit and integration tests

New files:
- src/utils/participant.py - Business logic utilities
- src/templates/participant/profile_edit.html - Profile edit form
- tests/unit/test_participant_utils.py - Unit tests for utilities
- tests/integration/test_participant_list.py - Integration tests for participant list
- tests/integration/test_profile_update.py - Integration tests for profile updates

Modified files:
- src/routes/participant.py - Added dashboard participant list and profile edit route
- src/templates/participant/dashboard.html - Added participant list section and edit link
- src/forms/participant.py - Added ProfileUpdateForm
- src/app.py - Added participant.profile_edit to setup check exemptions
- tests/conftest.py - Added exchange_factory, participant_factory, auth_participant fixtures

All tests passing. Phase 3.3 (reminder preferences) and 3.4 (withdrawal) remain to be implemented.

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

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

tests/conftest.py

@@ -75,3 +75,97 @@ def admin(db):
     db.session.add(admin)
     db.session.commit()
     return admin
+
+
+@pytest.fixture
+def exchange_factory(db):
+    """Factory for creating test exchanges.
+
+    Args:
+        db: Database instance.
+
+    Returns:
+        Function that creates and returns Exchange instances.
+    """
+    from datetime import UTC, datetime, timedelta
+
+    from src.models.exchange import Exchange
+
+    def _create(state="draft", **kwargs):
+        exchange = Exchange(
+            slug=kwargs.get("slug", Exchange.generate_slug()),
+            name=kwargs.get("name", "Test Exchange"),
+            budget=kwargs.get("budget", "$25-50"),
+            max_participants=kwargs.get("max_participants", 50),
+            registration_close_date=kwargs.get(
+                "registration_close_date", datetime.now(UTC) + timedelta(days=7)
+            ),
+            exchange_date=kwargs.get(
+                "exchange_date", datetime.now(UTC) + timedelta(days=14)
+            ),
+            timezone=kwargs.get("timezone", "UTC"),
+            state=state,
+        )
+        db.session.add(exchange)
+        db.session.commit()
+        return exchange
+
+    return _create
+
+
+@pytest.fixture
+def participant_factory(db, exchange_factory):
+    """Factory for creating test participants.
+
+    Args:
+        db: Database instance.
+        exchange_factory: Exchange factory fixture.
+
+    Returns:
+        Function that creates and returns Participant instances.
+    """
+    from src.models.participant import Participant
+
+    counter = {"value": 0}
+
+    def _create(exchange=None, **kwargs):
+        if not exchange:
+            exchange = exchange_factory()
+
+        counter["value"] += 1
+        participant = Participant(
+            exchange_id=exchange.id,
+            name=kwargs.get("name", f"Test Participant {counter['value']}"),
+            email=kwargs.get("email", f"test{counter['value']}@example.com"),
+            gift_ideas=kwargs.get("gift_ideas", "Test ideas"),
+            reminder_enabled=kwargs.get("reminder_enabled", True),
+            withdrawn_at=kwargs.get("withdrawn_at"),
+        )
+        db.session.add(participant)
+        db.session.commit()
+        return participant
+
+    return _create
+
+
+@pytest.fixture
+def auth_participant(client, exchange_factory, participant_factory):
+    """Create an authenticated participant session.
+
+    Args:
+        client: Flask test client.
+        exchange_factory: Exchange factory fixture.
+        participant_factory: Participant factory fixture.
+
+    Returns:
+        Authenticated participant instance.
+    """
+    exchange = exchange_factory(state="registration_open")
+    participant = participant_factory(exchange=exchange)
+
+    with client.session_transaction() as session:
+        session["user_id"] = participant.id
+        session["user_type"] = "participant"
+        session["exchange_id"] = exchange.id
+
+    return participant