[CHORE] Relocate module-level api_docs out of Java source tree

[aniebietafia]

Problem

Documentation markdown files (e.g., api_docs.md, api_doc.md, COUPON_SYSTEM_DOCUMENTATION.md) are located directly inside Java packages under src/main/java/com/xtraction/api/. This violates Maven conventions, clutters the package structure, and pollutes search results in IDEs.

Proposed Solution

Move all markdown documentation files out of the Java source tree and place them in the project's root /api_docs/ folder, structured by feature module name.

User Stories

• As a writer/developer, I want documentation files organized together in a dedicated root directory, rather than buried deep inside Java source folders.

Acceptance Criteria

• No .md files remain inside src/main/java/.
• All document files are moved and reorganized under /api_docs/ at the repository root.

Tasks

• Search the main directory for all .md files under src/main/java/.
• Move each file to the root /api_docs/ folder.
• Update any relative file links within the documents.