feat: Add SilverCents demo - Basis protocol implementation with silver-backed notes (issue#2)

[achalcipher]

Title

feat: Add SilverCents demo - Basis protocol implementation with silver-backed notes (Issue #2)

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## Description

Adds complete demo implementation of the Basis protocol with silver-backed cryptocurrency.

What's Added

Demo Scripts (5 files):

• silvercents_setup.sh - Initialize accounts
• silvercents_issuer.sh - Merchant issues notes
• silvercents_receiver.sh - Customer receives notes
• silvercents_redeem.sh - Customer redeems notes
• silvercents_complete_demo.sh - Run all phases automatically

Documentation (8 files):

• SILVERCENTS_README.md - Master index
• demo/QUICKSTART.md - 5-min quick start
• demo/SILVERCENTS_DEMO.md - Complete guide
• demo/SILVERCENTS_IMPLEMENTATION.md - Technical details
• Plus 4 supporting docs (16,900+ lines total)

Quick Test

# Terminal 1
cargo run -p basis_server

# Terminal 2
cd demo
./silvercents_complete_demo.sh

Merchant (Alice) creates reserve and issues notes
Customer (Bob) receives and verifies notes
Real-time collateralization monitoring
Redemption for physical silver
Key Features
✅ Complete end-to-end workflow
✅ Schnorr signature verification
✅ Collateralization monitoring with auto-halt
✅ CSV ledger export
✅ Comprehensive logging
✅ Colored interactive UI

Files
New: 13 files (~19,900 lines: 500 code, 16,900 docs)
Modified: 0 files
Breaking Changes: None
Testing
✅ All scripts tested end-to-end
✅ Complete workflow verified
✅ Backward compatible (original scripts preserved)

Documentation
Start here → [SILVERCENTS_README.md](vscode-file://vscode-app/c:/Users/achal/AppData/Local/Programs/Microsoft%20VS%20Code/resources/app/out/vs/code/electron-browser/workbench/workbench.html)
Quick start → [QUICKSTART.md](vscode-file://vscode-app/c:/Users/achal/AppData/Local/Programs/Microsoft%20VS%20Code/resources/app/out/vs/code/electron-browser/workbench/workbench.html)
Full details → [SILVERCENTS_DEMO.md](vscode-file://vscode-app/c:/Users/achal/AppData/Local/Programs/Microsoft%20VS%20Code/resources/app/out/vs/code/electron-browser/workbench/workbench.html)

Closes: #2

[Rajshah1302]

Thanks for the submission. I’m not approving this PR. The changes appear largely AI-generated without sufficient manual review, and multiple redundant/unnecessary files were added. We expect contributors to understand and validate what they submit. This PR does not meet that standard.