Add initial implementation of ePage application with Docker support

- Create main application logic with HTTP handlers for form submissions
- Implement Pushover API integration for sending messages
- Add unit tests for handlers and Pushover payload structure
- Include Dockerfile and docker-compose configuration for easy deployment
- Add example environment file and update README with setup instructions
- Create HTML templates for user interface

Dockerfile

@@ -0,0 +1,26 @@
+# Build stage
+FROM golang:1.23-alpine AS builder
+
+WORKDIR /app
+
+COPY go.mod go.sum ./
+RUN go mod download
+
+COPY . .
+
+RUN CGO_ENABLED=0 GOOS=linux go build -a -installsuffix cgo -o epage ./src
+
+# Runtime stage
+FROM alpine:latest
+
+RUN apk --no-cache add ca-certificates
+
+WORKDIR /root/
+
+COPY --from=builder /app/epage .
+COPY --from=builder /app/templates templates/
+COPY --from=builder /app/static static/
+
+EXPOSE 5000
+
+CMD ["./epage"]