Fix better-sqlite3 glibc/musl mismatch on Alpine (issue #6 followup)

prebuild-install downloads a prebuilt glibc .node binary for linux-x64 which
fails on Alpine (musl) with 'fcntl64: symbol not found'. Adding an explicit
npm rebuild --build-from-source step forces compilation against musl libc
inside the container, which is correct.

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

api/Dockerfile

@@ -5,7 +5,7 @@ RUN apk add --no-cache python3 make g++
 WORKDIR /app
 
 COPY package*.json ./
-RUN npm ci --omit=dev
+RUN npm ci --omit=dev && npm rebuild better-sqlite3 --build-from-source
 
 COPY . .