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>

src/routes/participant.py

@@ -17,7 +17,11 @@ from flask import (
 
 from src.app import db
 from src.decorators.auth import participant_required
-from src.forms.participant import MagicLinkRequestForm, ParticipantRegistrationForm
+from src.forms.participant import (
+    MagicLinkRequestForm,
+    ParticipantRegistrationForm,
+    ProfileUpdateForm,
+)
 from src.models.exchange import Exchange
 from src.models.magic_token import MagicToken
 from src.models.participant import Participant
@@ -341,10 +345,78 @@ def dashboard(id: int):  # noqa: A002
     if not participant:
         abort(404)
 
+    # Get list of active participants
+    from src.utils.participant import can_update_profile, get_active_participants
+
+    participants = get_active_participants(exchange.id)
+    can_edit = can_update_profile(participant)
+
     return render_template(
         "participant/dashboard.html",
         exchange=exchange,
         participant=participant,
+        participants=participants,
+        participant_count=len(participants),
+        can_edit_profile=can_edit,
+    )
+
+
+@participant_bp.route("/participant/profile/edit", methods=["GET", "POST"])
+@participant_required
+def profile_edit():
+    """Edit participant profile (name and gift ideas).
+
+    Only allowed before matching occurs.
+
+    Returns:
+        GET: Profile edit form
+        POST: Redirect to dashboard on success, or re-render form on error
+    """
+    from flask import current_app
+
+    # Get participant from session
+    participant = db.session.query(Participant).filter_by(id=session["user_id"]).first()
+    if not participant:
+        abort(404)
+
+    # Check if profile editing is allowed
+    from src.utils.participant import can_update_profile
+
+    if not can_update_profile(participant):
+        flash(
+            "Your profile is locked after matching. Contact the admin for changes.",
+            "error",
+        )
+        return redirect(url_for("participant.dashboard", id=participant.exchange_id))
+
+    # Create form with current values
+    form = ProfileUpdateForm(obj=participant)
+
+    if form.validate_on_submit():
+        try:
+            # Update participant
+            participant.name = form.name.data.strip()
+            participant.gift_ideas = (
+                form.gift_ideas.data.strip() if form.gift_ideas.data else None
+            )
+
+            db.session.commit()
+
+            flash("Your profile has been updated successfully.", "success")
+            return redirect(
+                url_for("participant.dashboard", id=participant.exchange_id)
+            )
+
+        except Exception as e:
+            db.session.rollback()
+            current_app.logger.error(f"Failed to update participant profile: {e}")
+            flash("Failed to update profile. Please try again.", "error")
+
+    return render_template(
+        "participant/profile_edit.html",
+        form=form,
+        participant=participant,
+        exchange=participant.exchange,
     )