refactor: restructure project from bookmann to shelf

- Rename project from 'bookmann' to 'shelf'
- Move all backend/ contents to root level (flatten structure)
- Update Go module name from 'bookmann' to 'shelf'
- Update all import paths to use new 'shelf' module
- Update Dockerfile to work without backend/ subdirectory
- Update docker-compose.yml to use new structure and rename containers
- Update .gitignore for new file paths
- Update README.md with new project name and structure
- Regenerate database code with new module imports

Dockerfile

@@ -0,0 +1,40 @@
+# Build stage
+FROM golang:1.25-alpine AS builder
+
+WORKDIR /app
+
+# Install sqlc
+RUN go install github.com/sqlc-dev/sqlc/cmd/sqlc@latest
+
+# Copy source code
+COPY . .
+
+# Download dependencies
+RUN go mod tidy
+
+# Generate sqlc code
+RUN sqlc generate
+
+# Build the application
+RUN CGO_ENABLED=0 GOOS=linux go build -a -installsuffix cgo -o main ./cmd/server
+
+# Final stage
+FROM alpine:latest
+
+RUN apk --no-cache add ca-certificates
+WORKDIR /root/
+
+# Copy the binary from builder stage
+COPY --from=builder /app/main .
+
+# Copy migrations (if needed for initialization)
+COPY --from=builder /app/migrations ./migrations
+
+# Copy templates
+COPY --from=builder /app/templates ./templates
+
+# Expose port
+EXPOSE 8765
+
+# Run the binary
+CMD ["./main"]