Add 6 more project pages: Flockstr, Shopstr, nostream, Penny, Universal Resolver, Cashu

New projects:
- Flockstr: Nostr calendar and events app (NIP-52)
- Shopstr: Decentralized marketplace with Cashu
- nostream: TypeScript Nostr relay with PostgreSQL
- Penny: Lightweight Solid pod browser
- Universal Resolver: Multi-method DID resolution
- Cashu: Chaumian ecash protocol for Bitcoin

Total pages: 87

Author: melvincarvalho

docs/projects/cashu/index.md

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+---
+title: Cashu
+description: Chaumian ecash for Bitcoin
+---
+
+# Cashu
+
+**Ecash protocol for Bitcoin.** Private, instant, and offline-capable digital cash.
+
+## Overview
+
+Cashu is a free and open-source Chaumian ecash protocol built on Bitcoin. It enables private, instant transactions using blinded tokens that can be sent without revealing sender identity to the mint.
+
+## How It Works
+
+```
+┌─────────────────────────────────────────────────────────┐
+│                    Cashu Flow                            │
+├─────────────────────────────────────────────────────────┤
+│                                                          │
+│  1. Deposit                                             │
+│     User pays Lightning invoice → Receives tokens       │
+│                                                          │
+│  2. Send                                                │
+│     User A sends tokens to User B (just a string!)     │
+│     Mint doesn't know who sent to whom                 │
+│                                                          │
+│  3. Receive                                             │
+│     User B redeems tokens at mint                       │
+│     Gets new tokens (breaks linkability)               │
+│                                                          │
+│  4. Withdraw                                            │
+│     User requests Lightning payout                      │
+│     Mint pays invoice, burns tokens                     │
+│                                                          │
+└─────────────────────────────────────────────────────────┘
+```
+
+## Key Features
+
+### Privacy
+
+```
+Traditional:
+Alice ──► Bank ──► Bob
+Bank sees: Alice sent $10 to Bob
+
+Cashu:
+Alice ──► Mint ──► Bob
+Mint sees: Someone deposited, someone withdrew
+Cannot link: Alice to Bob
+```
+
+Blinded signatures ensure the mint cannot track token flow.
+
+### Instant & Offline
+
+| Feature | Description |
+|---------|-------------|
+| **Instant** | No blockchain confirmation |
+| **Offline** | Send tokens without internet |
+| **Free** | No transaction fees |
+
+Tokens are just strings — send via text, QR, Nostr DM.
+
+### Token Format
+
+```
+cashuAeyJ0b2tlbiI6W3sicHJvb2ZzIjpbeyJpZCI6IjAwY...
+```
+
+A Cashu token is a base64-encoded string containing:
+- Mint URL
+- Proofs (blinded signatures)
+- Amount
+
+## Protocol
+
+### Nut Specifications
+
+Cashu is defined by NUTs (Notation, Usage, and Terminology):
+
+| NUT | Feature |
+|-----|---------|
+| NUT-00 | Token format |
+| NUT-01 | Mint public keys |
+| NUT-02 | Keysets |
+| NUT-03 | Swap tokens |
+| NUT-04 | Mint tokens |
+| NUT-05 | Melt tokens |
+| NUT-06 | Mint info |
+| NUT-07 | Token state |
+| NUT-08 | Lightning payments |
+
+### API Endpoints
+
+```
+POST /v1/mint/quote/bolt11    # Get minting quote
+POST /v1/mint/bolt11          # Mint tokens
+POST /v1/swap                 # Swap tokens
+POST /v1/melt/quote/bolt11    # Get melting quote
+POST /v1/melt/bolt11          # Melt (withdraw)
+GET  /v1/keys                 # Mint public keys
+GET  /v1/info                 # Mint information
+```
+
+## Using Cashu
+
+### Wallets
+
+| Wallet | Platform |
+|--------|----------|
+| **Nutstash** | Web |
+| **eNuts** | Mobile |
+| **Minibits** | Mobile |
+| **Cashu.me** | Web |
+| **Nutshell** | CLI |
+
+### Nostr Integration
+
+Cashu works great with Nostr:
+- Send tokens via DMs (NIP-04)
+- Zap alternatives
+- Shopstr payments
+- Ecash tips
+
+## For Developers
+
+### JavaScript
+
+```javascript
+import { CashuMint, CashuWallet } from '@cashu/cashu-ts';
+
+// Connect to mint
+const mint = new CashuMint('https://mint.example.com');
+const wallet = new CashuWallet(mint);
+
+// Get minting quote
+const quote = await wallet.getMintQuote(1000);
+
+// After paying Lightning invoice...
+const tokens = await wallet.mintTokens(1000, quote.quote);
+
+// Send tokens (just a string)
+const tokenString = wallet.getEncodedToken(tokens);
+
+// Receive tokens
+const received = await wallet.receive(tokenString);
+```
+
+### Running a Mint
+
+```bash
+# Using Nutshell
+git clone https://github.com/cashubtc/nutshell.git
+cd nutshell
+
+# Configure
+cp .env.example .env
+# Edit .env with your LN node details
+
+# Run
+docker-compose up
+```
+
+### Mint Backends
+
+| Backend | Description |
+|---------|-------------|
+| **LND** | Lightning Network Daemon |
+| **CLN** | Core Lightning |
+| **LNbits** | Account system |
+
+## Trust Model
+
+```
+┌─────────────────────────────────────────────────────────┐
+│                   Trust Model                            │
+├─────────────────────────────────────────────────────────┤
+│                                                          │
+│  What mint CAN do:                                      │
+│  ├── Refuse to honor tokens (rug pull)                 │
+│  └── Inflate supply (print fake tokens)                │
+│                                                          │
+│  What mint CANNOT do:                                   │
+│  ├── See who sent to whom                              │
+│  ├── Link deposits to withdrawals                      │
+│  └── Censor specific users                             │
+│                                                          │
+│  Mitigations:                                           │
+│  ├── Use reputable mints                               │
+│  ├── Don't hold large balances                         │
+│  └── Use multiple mints                                │
+│                                                          │
+└─────────────────────────────────────────────────────────┘
+```
+
+## Comparison
+
+| Feature | Cashu | Lightning | On-chain |
+|---------|-------|-----------|----------|
+| Privacy | High | Medium | Low |
+| Speed | Instant | Instant | ~10min |
+| Offline | Yes | No | No |
+| Trust | Mint | Routing | Miners |
+| Fees | None | Small | Variable |
+
+## Use Cases
+
+### Private Payments
+
+Send money without revealing your identity.
+
+### Nostr Tipping
+
+Tip content creators privately via DMs.
+
+### Marketplaces
+
+Shopstr uses Cashu for private commerce.
+
+### Gift Cards
+
+Send digital cash to anyone with a link.
+
+## Links
+
+- **Website:** [cashu.space](https://cashu.space/)
+- **Protocol:** [github.com/cashubtc/nuts](https://github.com/cashubtc/nuts)
+- **Nutshell:** [github.com/cashubtc/nutshell](https://github.com/cashubtc/nutshell)
+- **cashu-ts:** [github.com/cashubtc/cashu-ts](https://github.com/cashubtc/cashu-ts)
+
+## See Also
+
+- [Nostr Protocol](/protocols/nostr) — The protocol
+- [Shopstr](/projects/shopstr) — Marketplace using Cashu
+- [Alby](/projects/alby) — Lightning wallet
+- [Amber](/projects/amber) — Nostr signing