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/lib/hooks/use-residences.ts

@@ -1,7 +1,7 @@
 "use client";
 
 import { useQuery, useMutation, useQueryClient } from '@tanstack/react-query';
-import * as residencesApi from '@/lib/api/residences';
+import { useDataProvider } from '@/lib/demo/data-provider-context';
 import type { CreateResidenceRequest, UpdateResidenceRequest } from '@/lib/api/residences';
 
 // ---------------------------------------------------------------------------
@@ -9,16 +9,19 @@ import type { CreateResidenceRequest, UpdateResidenceRequest } from '@/lib/api/r
 // ---------------------------------------------------------------------------
 
 export function useResidences() {
+  const { residences } = useDataProvider();
   return useQuery({
     queryKey: ['residences'],
-    queryFn: () => residencesApi.getMyResidences(),
+    queryFn: () => residences.getMyResidences(),
+    select: (data) => (Array.isArray(data) ? data : []),
   });
 }
 
 export function useResidence(id: number) {
+  const { residences } = useDataProvider();
   return useQuery({
     queryKey: ['residences', id],
-    queryFn: () => residencesApi.getResidence(id),
+    queryFn: () => residences.get(id),
     enabled: !!id,
   });
 }
@@ -29,9 +32,10 @@ export function useResidence(id: number) {
 
 export function useCreateResidence() {
   const queryClient = useQueryClient();
+  const { residences } = useDataProvider();
   return useMutation({
     mutationFn: (data: CreateResidenceRequest) =>
-      residencesApi.createResidence(data),
+      residences.create(data),
     onSuccess: () => {
       queryClient.invalidateQueries({ queryKey: ['residences'] });
     },
@@ -40,9 +44,10 @@ export function useCreateResidence() {
 
 export function useUpdateResidence(id: number) {
   const queryClient = useQueryClient();
+  const { residences } = useDataProvider();
   return useMutation({
     mutationFn: (data: UpdateResidenceRequest) =>
-      residencesApi.updateResidence(id, data),
+      residences.update(id, data),
     onSuccess: () => {
       queryClient.invalidateQueries({ queryKey: ['residences'] });
       queryClient.invalidateQueries({ queryKey: ['residences', id] });
@@ -52,8 +57,9 @@ export function useUpdateResidence(id: number) {
 
 export function useDeleteResidence() {
   const queryClient = useQueryClient();
+  const { residences } = useDataProvider();
   return useMutation({
-    mutationFn: (id: number) => residencesApi.deleteResidence(id),
+    mutationFn: (id: number) => residences.delete(id),
     onSuccess: () => {
       queryClient.invalidateQueries({ queryKey: ['residences'] });
     },