Add public read API slice

[wauputr4]

Summary

• Add repository modules for public organizations, posts, and impact reports.
• Add public read endpoints for organization profiles, organization posts, organization impact reports, global posts, and post detail.
• Add kelompok seed demo plus Makefile/docs updates so the public MVP has data to render.

Public endpoints

GET /api/v1/organizations
GET /api/v1/organizations/{slug}
GET /api/v1/organizations/{slug}/posts
GET /api/v1/organizations/{slug}/impact-reports
GET /api/v1/posts
GET /api/v1/posts/{slug}

Validation

• make test
• go mod tidy
• go run ./cmd/kelompok help
• git diff --check
• Ran kelompok seed demo against the dev database
• Smoke-tested /readyz, /api/v1/organizations?limit=1, /api/v1/organizations/gerakan-hijau-nusantara/posts, /api/v1/organizations/gerakan-hijau-nusantara/impact-reports, and /api/v1/posts/first-neighborhood-climate-lab against the local API connected to dev DB

Refs #3

[gemini-code-assist]

Code Review

This pull request introduces the initial public read API for organizations, posts, and impact reports, including new repository layers, HTTP handlers with pagination, and a CLI command for seeding demo data. Documentation and the Makefile have been updated to reflect these additions. The review feedback suggests several technical refinements: using COALESCE in SQL queries to prevent scanning errors on NULL values, pre-allocating slice capacities to optimize memory usage, and refactoring a duplicated helper function into a shared package to improve maintainability.

[chatgpt-codex-connector]

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