feat: GeoScene frontend POC + Docker deploy for remote host

Migrate maps to @geoscene/core, polish monitoring/alerts UX, fix timeline
basemap flicker and district alert regions, and ship compose/nginx Docker
deploy assets with CBPOA_ROOT data mounts.

Co-authored-by: Cursor <cursoragent@cursor.com>

deploy/frontend/.dockerignore

@@ -3,4 +3,4 @@ node_modules
 *.md
 tests
 .env*
-dist
+dist

deploy/frontend/Dockerfile

@@ -5,16 +5,11 @@ FROM node:20-alpine AS builder
 
 WORKDIR /app
 
-# Copy package files
 COPY package.json pnpm-lock.yaml ./
-
-# Install dependencies (using pnpm since lock file is pnpm-lock.yaml)
 RUN npm install -g pnpm && pnpm install --frozen-lockfile
 
-# Copy source code
 COPY . .
-
-# Build the application
+ENV VITE_API_URL=/api
 RUN pnpm run build
 
 # =============================================================================
@@ -22,15 +17,10 @@ RUN pnpm run build
 # =============================================================================
 FROM nginx:alpine AS production
 
-# Copy custom nginx config for SPA routing
-COPY --from=builder /app/nginx.conf /etc/nginx/conf.d/default.conf
-
-# Copy built assets from builder
+COPY nginx.conf /etc/nginx/conf.d/default.conf
 COPY --from=builder /app/dist /usr/share/nginx/html
 
-# Expose port 80
 EXPOSE 80
 
-# Health check for nginx
 HEALTHCHECK --interval=30s --timeout=3s --start-period=5s --retries=3 \
-    CMD wget --no-redirect --quiet --tries=1 --spider http://localhost/ || exit 1
+    CMD wget --no-redirect --quiet --tries=1 --spider http://localhost/ || exit 1