[Hard]: Add CI quality gates for frontend and subgraph workflows

[AnirudhSinghRajora]

Context and Motivation

Repository currently lacks strong automated pull request checks for core quality gates.

Architecture Proposal

Add CI workflow for frontend install/build/test.
Add CI workflow for subgraph codegen/build/test.
Configure trigger on pull requests.
Keep workflows readable and fast.
Document CI expectations in project docs.

Cross-Repo Scope

.github
event-dappp/package.json
event-ticketinng/package.json
README.md

Acceptance Criteria

• CI runs automatically on pull requests
• Frontend install, build, and test checks execute in CI
• Subgraph codegen, build, and test checks execute in CI
• CI usage and expected checks are documented

Verification and Test Strategy

Open a test pull request.
Verify workflows start automatically.
Confirm all required checks complete successfully.
Confirm failed checks block merge if branch protection is enabled.

Dependencies or Blockers

Requires GitHub Actions permissions enabled.
Optional branch protection setup for required checks.