update database driver to modernc.org/sqlite and add Dockerfile with multi-stage build

.gitignore

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+.idea/

Dockerfile

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+FROM node:22.14.0 AS frontend
+
+WORKDIR /frontend
+ADD frontend/ ./
+RUN npm install && npm run build
+
+FROM golang:1.24.4 AS backend
+
+ENV CGO_ENABLED=0
+
+WORKDIR /backend
+ADD backend/ .
+
+RUN go mod download
+RUN go build -o /backend/app
+
+FROM alpine AS runtime
+
+WORKDIR /app
+
+COPY --from=frontend /frontend/dist /app/dist
+COPY --from=backend /backend/app /app/app
+
+EXPOSE 8000
+
+ENTRYPOINT ["/app/app"]