feat: Phase 4-5 — demo mode, polish, deploy, and bug fixes

Add demo mode with mock data provider, Docker deployment, Playwright
tests, PostHog analytics, error boundaries, and SEO metadata. Fix
residences API response unwrapping, kanban drag-and-drop with optimistic
updates, trailing slash proxy redirects, and column name mismatches with
Go API.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/components/tasks/task-form.tsx

@@ -49,12 +49,12 @@ export function TaskForm({ task, onSubmit, isSubmitting }: TaskFormProps) {
   const { data: priorities } = useTaskPriorities();
   const { data: frequencies } = useTaskFrequencies();
 
-  const residenceItems = (residences ?? []).map((r) => ({
+  const residenceItems = (Array.isArray(residences) ? residences : []).map((r) => ({
     id: r.residence.id,
     name: r.residence.name,
   }));
 
-  const contractorItems = (contractors ?? []).map((c) => ({
+  const contractorItems = (Array.isArray(contractors) ? contractors : []).map((c) => ({
     id: c.id,
     name: c.company ? `${c.name} (${c.company})` : c.name,
   }));