Switch API base image from Alpine to node:20-slim (Debian)

better-sqlite3's prebuild-install downloads prebuilt glibc binaries for
linux-x64, which fail on Alpine's musl libc with 'fcntl64: symbol not found'.
npm_config_build_from_source was not being honoured. Switching to a
glibc-based image sidesteps the issue entirely; homelab image size is fine.

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

api/Dockerfile

@@ -1,13 +1,11 @@
-FROM node:20-alpine
+FROM node:20-slim
 
-RUN apk add --no-cache python3 make g++
+RUN apt-get update -qq && apt-get install -y -qq python3 make g++ && rm -rf /var/lib/apt/lists/*
 
 WORKDIR /app
 
 COPY package*.json ./
-# build_from_source tells prebuild-install to compile better-sqlite3 against
+RUN npm ci --omit=dev
-# musl (Alpine) instead of downloading a prebuilt glibc binary
-RUN npm_config_build_from_source=true npm ci --omit=dev
 
 COPY . .