Migrate portal backend builds from Task to `build.sh`

[rashmithachamikara]

Description

Currently, the portal backend utilizes Task instead of build.sh. The build system should probably depend on the deployment direction

What is Task

Go-Task (or simply Task) is a modern, cross-platform task runner and build tool written in Go that uses YAML-based configuration files to simplify running terminal commands, similar to GNU Make.

Differences

It is required to migrate the portal backend’s Taskfile.yml workflow to a build.sh workflow for consistency with the consent server.

Area	Portal backend	Consent server
Primary command	cd portal/backend && task build	From repo root: ./build.sh build [OS] [ARCH]
Underlying Go command	go build -o bin/portal-backend[.exe] ./cmd/server	GOOS=... GOARCH=... CGO_ENABLED=0 go build -ldflags ... -o ../target/server/consent-server ./cmd/server
Output	portal/backend/bin/portal-backend	target/server/consent-server
Cross-compilation	Host OS only; adds .exe on Windows	Explicit OS/architecture arguments
Runtime assets	Binary only	Copies config, startup script, DB scripts, API specs, README, and version

Key decisions to be made

• Use a dedicated script for the portal backend or extend the root build.sh.
• Define the command interface, binary name, and output directory.
• Use a separate config YAML for the portal (commonly at portal root) or in portal-backend.
• Decide whether cross-compilation and distribution packaging are required.
• Decide how Windows developers will run the script. (For example, ThunderID maintains a PowerShell version for each script)
• Determine whether to retain Task temporarily as a compatibility wrapper.
• Decide which of the current commands (lint, fmt:check, test) to support in the new build.sh.
• Decide which commands to be automatically executed on build ((lint, fmt:check, test)

Affected Product Version:

Current feature/portal branch

OS, DB, other environment details and versions:

Go 1.26.x; Linux, macOS, and Windows through Git Bash or WSL.

Steps to reproduce:

1. Run task build from portal/backend.
2. Compare it with ./build.sh build from the repository root.
3. Observe that the two services use inconsistent build commands and artifact layouts.