Add Axum backend, Dockerfiles, and K8s deployment manifests

- Axum backend server: health check, transfer matrix cache (base64 BYTEA),
  route cache (JSONB), CORS, gzip compression, tracing
- Postgres schema: transfer_matrices + cached_routes tables with upserts
- Dockerfile.frontend: 3-stage (wasm-pack → SvelteKit → nginx:alpine)
- Dockerfile.backend: 2-stage (rust build → debian:bookworm-slim)
- nginx.conf: SPA fallback, WASM mime type, /api proxy to backend
- docker-compose.yml: Postgres + backend for local development
- K8s manifests: namespace, frontend/backend deployments with services,
  ingress routing, health probes, secret-based DATABASE_URL

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Dockerfile.frontend

@@ -0,0 +1,24 @@
+# Stage 1: Build WASM package
+FROM rust:1.82-slim AS wasm-builder
+RUN apt-get update && apt-get install -y curl pkg-config libssl-dev && rm -rf /var/lib/apt/lists/*
+RUN curl https://rustwasm.github.io/wasm-pack/installer/init.sh -sSf | sh
+WORKDIR /app
+COPY Cargo.toml Cargo.lock ./
+COPY crates/ crates/
+RUN wasm-pack build crates/mass-driver-wasm --target web --out-dir pkg
+
+# Stage 2: Build SvelteKit frontend
+FROM node:22-slim AS frontend-builder
+WORKDIR /app/frontend
+COPY frontend/package.json frontend/package-lock.json ./
+RUN npm ci
+COPY --from=wasm-builder /app/crates/mass-driver-wasm/pkg ./node_modules/mass-driver-wasm
+COPY frontend/ ./
+RUN npm run build
+
+# Stage 3: Serve with nginx
+FROM nginx:alpine
+COPY --from=frontend-builder /app/frontend/build /usr/share/nginx/html
+COPY nginx.conf /etc/nginx/nginx.conf
+EXPOSE 80
+CMD ["nginx", "-g", "daemon off;"]