Fix frontend unable to load weather data by using relative API URL

NEXT_PUBLIC_API_URL was only set at runtime via k8s ConfigMap, but Next.js
inlines NEXT_PUBLIC_* vars at build time. The fallback localhost:8080 URL was
baked into the JS bundle, causing all browser requests to fail. Changed default
to relative /api/v1 which routes correctly through the Ingress. Also updates
Dockerfile ENV syntax and k8s frontend port to 8080.

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

frontend/Dockerfile

@@ -13,8 +13,8 @@ COPY --from=deps /app/node_modules ./node_modules
 COPY . .
 
 # Set production environment
-ENV NEXT_TELEMETRY_DISABLED 1
-ENV NODE_ENV production
+ENV NEXT_TELEMETRY_DISABLED=1
+ENV NODE_ENV=production
 
 RUN npm run build
 
@@ -22,8 +22,8 @@ RUN npm run build
 FROM node:20-alpine AS runner
 WORKDIR /app
 
-ENV NODE_ENV production
-ENV NEXT_TELEMETRY_DISABLED 1
+ENV NODE_ENV=production
+ENV NEXT_TELEMETRY_DISABLED=1
 
 RUN addgroup --system --gid 1001 nodejs
 RUN adduser --system --uid 1001 nextjs
@@ -42,8 +42,8 @@ USER nextjs
 
 EXPOSE 3000
 
-ENV PORT 3000
-ENV HOSTNAME "0.0.0.0"
+ENV PORT=3000
+ENV HOSTNAME="0.0.0.0"
 
 CMD ["node", "server.js"]