feat: Email Team button + custom-email dialog on project page

Adds a PROJECT_TEAM recipient type to the message router (resolver
returns team members + project lead) and an "Email Team" button on
the admin project detail page that opens a self-contained dialog
matching the look of /admin/messages: subject, body (pre-filled
with "Hello [Project Title] team,\n\n"), live HTML preview iframe,
"Send test to me" + "Send to N" actions.

The composer reuses the existing message.previewEmail and
message.send tRPC procedures end-to-end — no parallel email
infrastructure introduced.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/app/(admin)/admin/projects/[id]/page.tsx

@@ -75,7 +75,9 @@ import {
   Eye,
   Plus,
   X,
+  Mail,
 } from 'lucide-react'
+import { ProjectEmailDialog } from '@/components/admin/project-email-dialog'
 import { toast } from 'sonner'
 import { formatDateOnly } from '@/lib/utils'
 import { getCountryName, getCountryFlag } from '@/lib/countries'
@@ -161,6 +163,7 @@ function ProjectDetailContent({ projectId }: { projectId: string }) {
 
   // State for remove member confirmation
   const [removingMemberId, setRemovingMemberId] = useState<string | null>(null)
+  const [emailDialogOpen, setEmailDialogOpen] = useState(false)
 
   const addTeamMember = trpc.project.addTeamMember.useMutation({
     onSuccess: () => {
@@ -269,14 +272,29 @@ function ProjectDetailContent({ projectId }: { projectId: string }) {
           </div>
         </div>
 
-        <Button variant="outline" asChild>
-          <Link href={`/admin/projects/${projectId}/edit`}>
-            <Edit className="mr-2 h-4 w-4" />
-            Edit
-          </Link>
-        </Button>
+        <div className="flex items-center gap-2">
+          <Button variant="outline" onClick={() => setEmailDialogOpen(true)}>
+            <Mail className="mr-2 h-4 w-4" />
+            Email Team
+          </Button>
+          <Button variant="outline" asChild>
+            <Link href={`/admin/projects/${projectId}/edit`}>
+              <Edit className="mr-2 h-4 w-4" />
+              Edit
+            </Link>
+          </Button>
+        </div>
       </div>
 
+      {project && (
+        <ProjectEmailDialog
+          open={emailDialogOpen}
+          onClose={() => setEmailDialogOpen(false)}
+          projectId={project.id}
+          projectTitle={project.title}
+        />
+      )}
+
       <Separator />
 
       {/* Stats Grid */}