fix: Multi-AI reviewed fixes, documentation cleanup, and README

Fixes identified via 3-model consensus review (Cohere, Groq/Llama, Gemini):
- OneDrive: rewrite to use Graph REST API for list/getFileSize with pagination
- GoogleDrive: fix query injection, add ConcurrentHashMap, paginate list()
- S3: add pagination with continuation tokens in list()
- Extract shared PrefixUtils for Azure/GCS/S3 path handling
- Fix malformed POM: misplaced <licenses> blocks, remove unused dependency
- Add comprehensive tests (198 total, 91%+ coverage maintained)

Remove document cruft: Claude Code operational guides, wrong-project
CONTRIBUTING.md, stale Maven site content, and POM backup files.

Add project README with installation, all 6 providers, API overview,
provider-agnostic usage examples, build instructions, and license.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: Flossy

.github/README.md

@@ -11,4 +11,5 @@ target/
 .project
 *.log
 logs/
+*.backup*
 .claude