fix(docker): switch builder to node:20 to resolve native module compilation failure

[Copilot]

Docker — Build Images was failing because @solana/wallet-adapter-wallets pulls in hardware wallet adapters (e.g. Ledger) that depend on the usb native module, which requires Python3/make/g++ — none of which exist in node:20-alpine.

Changes

• Builder base image: node:20-alpine → node:20 (Debian-based) in both Dockerfile.frontend and Dockerfile.backend. The full node:20 image ships with the complete build toolchain needed for native module compilation via node-gyp. Runner stages remain node:20-alpine.
• Reproducible installs: Added COPY package-lock.json and switched builder installs from npm install to npm ci to lock dependency resolution.

# Before
FROM node:20-alpine AS builder
COPY package.json ./
RUN npm install --workspace=frontend

# After
FROM node:20 AS builder
COPY package.json package-lock.json ./
RUN npm ci --workspace=frontend

# Runner stays lean
FROM node:20-alpine AS runner

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