Backlog: Add contributor-facing first good tasks index

[kishorjakkula]

Goal

Help new contributors find approachable work and understand how to contribute without needing deep project history.

Expected Scope

• Add docs/FIRST_GOOD_TASKS.md or a README section linking beginner-friendly issues.
• Group tasks by docs, tests, frontend, backend API, product packs, and dev tooling.
• Include setup prerequisites and expected validation commands for each task type.
• Link to docs/AI_CONTRIBUTOR_PROCESS.md, docs/PROJECT_CONTEXT.md, and task note conventions.
• Optionally add GitHub labels such as good first issue, help wanted, docs, and tests.

Acceptance Criteria

• New contributors can identify 5-10 suitable starter tasks.
• Each starter task has clear expected files, validation commands, and acceptance criteria.
• README links to the index.

Suggested Validation

• Documentation review.
• Confirm listed issues are current and realistically scoped.