feat: make responsiblePerson required on project creation/edit

- Zod schema: responsiblePerson now min(1) required, no longer optional
- ProjectModal: required indicator (*), HTML required attribute, no undefined fallback
- ProjectWizard: same fix for create flow
- Existing projects with null responsiblePerson still work (DB allows null)
- Validation enforced at API boundary on new creates/updates

Co-Authored-By: claude-flow <ruv@ruv.net>

apps/web/src/components/projects/ProjectModal.tsx

@@ -204,7 +204,7 @@ export function ProjectModal({ project, onClose }: ProjectModalProps) {
           startDate: new Date(form.startDate),
           endDate: new Date(form.endDate),
           status: form.status as unknown as ProjectStatus,
-          responsiblePerson: form.responsiblePerson.trim() || undefined,
+          responsiblePerson: form.responsiblePerson.trim(),
           ...(form.color ? { color: form.color } : {}),
           ...(form.utilizationCategoryId ? { utilizationCategoryId: form.utilizationCategoryId } : {}),
           ...(form.clientId ? { clientId: form.clientId } : {}),
@@ -223,7 +223,7 @@ export function ProjectModal({ project, onClose }: ProjectModalProps) {
         status: form.status as unknown as ProjectStatus,
         staffingReqs: [],
         dynamicFields: {},
-        responsiblePerson: form.responsiblePerson.trim() || undefined,
+        responsiblePerson: form.responsiblePerson.trim(),
         ...(form.color ? { color: form.color } : {}),
         ...(form.utilizationCategoryId ? { utilizationCategoryId: form.utilizationCategoryId } : {}),
         ...(form.clientId ? { clientId: form.clientId } : {}),
@@ -521,8 +521,8 @@ export function ProjectModal({ project, onClose }: ProjectModalProps) {
                 </div>
                 <div>
                   <label className={labelClass} htmlFor="responsiblePerson">
-                    Responsible Person
-                    <InfoTooltip content="Project lead or account manager responsible for this project." />
+                    Responsible Person <span className="text-red-500">*</span>
+                    <InfoTooltip content="Project lead or account manager responsible for this project. Required." />
                   </label>
                   <input
                     id="responsiblePerson"
@@ -530,6 +530,7 @@ export function ProjectModal({ project, onClose }: ProjectModalProps) {
                     value={form.responsiblePerson}
                     onChange={(e) => setField("responsiblePerson", e.target.value)}
                     placeholder="Name or EID"
+                    required
                     className={inputClass}
                   />
                 </div>