feat(docker): Preseed cities database and fix multi-arch builds

Bake the GeoNames cities database into the image at build time instead
of relying on host-mounted sqlite files, and fix the Go build stage to
cross-compile for the requested target platform instead of hardcoding
amd64 (was silently broken for arm64 builds).

Dockerfile

@@ -1,4 +1,7 @@
-FROM golang:1.25-bookworm AS builder
+FROM --platform=$BUILDPLATFORM golang:1.25-bookworm AS builder
+
+ARG TARGETOS
+ARG TARGETARCH
 
 WORKDIR /src
 
@@ -6,7 +9,13 @@ COPY go.mod go.sum ./
 RUN go mod download
 
 COPY . .
-RUN CGO_ENABLED=0 GOOS=linux GOARCH=amd64 go build -trimpath -ldflags="-s -w" -o /out/prayertimes .
+RUN CGO_ENABLED=0 GOOS=$TARGETOS GOARCH=$TARGETARCH go build -trimpath -ldflags="-s -w" -o /out/prayertimes .
+
+FROM --platform=$BUILDPLATFORM python:3.12-slim AS seeder
+
+WORKDIR /seed
+COPY scripts/seed_cities.py .
+RUN python3 seed_cities.py --db /data/prayertimes.sqlite3
 
 FROM debian:bookworm-slim
 
@@ -17,6 +26,7 @@ RUN apt-get update \
 WORKDIR /app
 
 COPY --from=builder /out/prayertimes /usr/local/bin/prayertimes
+COPY --from=seeder /data/prayertimes.sqlite3 /data/prayertimes.sqlite3
 
 ENV PORT=8000
 ENV DB_PATH=/data/prayertimes.sqlite3

docker-compose.yml

@@ -8,9 +8,4 @@ services:
       - "8000:8000"
     environment:
       PORT: "8000"
-      DB_PATH: "/data/prayertimes.sqlite3"
-    volumes:
-      - ./prayertimes.sqlite3:/data/prayertimes.sqlite3
-      - ./prayertimes.sqlite3-wal:/data/prayertimes.sqlite3-wal
-      - ./prayertimes.sqlite3-shm:/data/prayertimes.sqlite3-shm
     restart: unless-stopped