Add project creation from team dashboard and update seed data

- Add project creation modal to TeamDashboardPage with team_id assignment
- Update createProject API function to accept optional team_id
- Update seed data to create a "Demo Team" and assign all projects to it
- Admin user is added as team owner when present

frontend/src/pages/TeamDashboardPage.tsx

@@ -1,7 +1,7 @@
 import { useState, useEffect, useCallback } from 'react';
 import { Link, useParams, useNavigate } from 'react-router-dom';
 import { TeamDetail, Project, PaginatedResponse } from '../types';
-import { getTeam, listTeamProjects } from '../api';
+import { getTeam, listTeamProjects, createProject } from '../api';
 import { useAuth } from '../contexts/AuthContext';
 import { Badge } from '../components/Badge';
 import { Breadcrumb } from '../components/Breadcrumb';
@@ -15,6 +15,9 @@ function TeamDashboardPage() {
   const [projects, setProjects] = useState<PaginatedResponse<Project> | null>(null);
   const [loading, setLoading] = useState(true);
   const [error, setError] = useState<string | null>(null);
+  const [showProjectForm, setShowProjectForm] = useState(false);
+  const [newProject, setNewProject] = useState({ name: '', description: '', is_public: true });
+  const [creating, setCreating] = useState(false);
 
   const loadTeamData = useCallback(async () => {
     if (!slug) return;
@@ -38,6 +41,22 @@ function TeamDashboardPage() {
     loadTeamData();
   }, [loadTeamData]);
 
+  async function handleCreateProject(e: React.FormEvent) {
+    e.preventDefault();
+    if (!team) return;
+    try {
+      setCreating(true);
+      const project = await createProject({ ...newProject, team_id: team.id });
+      setNewProject({ name: '', description: '', is_public: true });
+      setShowProjectForm(false);
+      navigate(`/project/${project.name}`);
+    } catch (err) {
+      setError(err instanceof Error ? err.message : 'Failed to create project');
+    } finally {
+      setCreating(false);
+    }
+  }
+
   if (loading) {
     return (
       <div className="team-dashboard">
@@ -124,13 +143,64 @@ function TeamDashboardPage() {
         </div>
       )}
 
+      {showProjectForm && (
+        <div className="modal-overlay" onClick={() => setShowProjectForm(false)}>
+          <div className="modal-content" onClick={e => e.stopPropagation()}>
+            <h2>Create New Project</h2>
+            <form onSubmit={handleCreateProject}>
+              <div className="form-group">
+                <label htmlFor="project-name">Project Name</label>
+                <input
+                  id="project-name"
+                  type="text"
+                  value={newProject.name}
+                  onChange={e => setNewProject({ ...newProject, name: e.target.value })}
+                  placeholder="my-project"
+                  required
+                  autoFocus
+                />
+              </div>
+              <div className="form-group">
+                <label htmlFor="project-description">Description (optional)</label>
+                <textarea
+                  id="project-description"
+                  value={newProject.description}
+                  onChange={e => setNewProject({ ...newProject, description: e.target.value })}
+                  placeholder="What is this project for?"
+                  rows={3}
+                />
+              </div>
+              <div className="form-group checkbox-group">
+                <label>
+                  <input
+                    type="checkbox"
+                    checked={newProject.is_public}
+                    onChange={e => setNewProject({ ...newProject, is_public: e.target.checked })}
+                  />
+                  Public project
+                </label>
+                <span className="form-hint">Public projects are visible to everyone</span>
+              </div>
+              <div className="form-actions">
+                <button type="button" className="btn btn-secondary" onClick={() => setShowProjectForm(false)}>
+                  Cancel
+                </button>
+                <button type="submit" className="btn btn-primary" disabled={creating}>
+                  {creating ? 'Creating...' : 'Create Project'}
+                </button>
+              </div>
+            </form>
+          </div>
+        </div>
+      )}
+
       <div className="team-section">
         <div className="section-header">
           <h2>Projects</h2>
           {isAdminOrOwner && (
-            <Link to="/" className="btn btn-primary btn-sm">
+            <button className="btn btn-primary btn-sm" onClick={() => setShowProjectForm(true)}>
               + New Project
-            </Link>
+            </button>
           )}
         </div>
 
@@ -138,7 +208,9 @@ function TeamDashboardPage() {
           <div className="empty-state">
             <p>No projects in this team yet.</p>
             {isAdminOrOwner && (
-              <p className="empty-hint">Create a project and assign it to this team to get started.</p>
+              <button className="btn btn-primary" onClick={() => setShowProjectForm(true)}>
+                Create Project
+              </button>
             )}
           </div>
         ) : (