docs: repair broken deployment and compression links - #18339

Summary

Repairs broken and misleading deployment and compression links identified from the link-checker report in #18160 and the affected mirrored documentation:

• points the Chinese and English PP-OCRv5 Android release notes to the versioned v3.0.2 guides, rather than the current PP-OCRv6 Android page;
• replaces both Chinese and English distillation_model.py references with version-aware GitHub source links that resolve correctly in main and release documentation builds;
• removes the duplicated English pruning explanation and pins the pruning references to the exact PaddleSlim 2.0-alpha sensitivity-based pruning section;
• applies the same pruning-link and Markdown fixes to the mirrored deployment READMEs.

Refs #18160

Verification

• Confirmed the Chinese and English v3.0.2 Android guides explicitly support PP-OCRv5_mobile.
• Confirmed the PaddleSlim link resolves to the 2.3 基于敏感度剪裁卷积网络 section.
• pytest -q tests/tools/test_docs_github_links.py passes (3 tests).
• python tools/check_docs_github_links.py --root docs --repo-slug PaddlePaddle/PaddleOCR --forbidden-ref main --forbidden-ref master passes.
• ENABLE_GIT_PLUGINS=false mkdocs build -f mkdocs-ci.yml passes.
• git diff --check passes.

This is a documentation-only change with no runtime or API impact.