feat: Add zap command for sending Bitcoin Lightning tips

- Implemented the `zap` command in the CLI to allow users to send sats to a user, event, or snippet using a NIP-60 wallet.
- Created a new `zap.ts` file to handle the command logic and integrated it into the MCP server.
- Added wallet balance command to check the balance of a user's wallet.
- Enhanced the MCP server to register the new zap command and wallet balance command.
- Introduced caching for wallets to optimize performance and reduce redundant network requests.
- Updated database schema to include snippets table for storing code snippets.
- Improved logging functionality for better debugging and tracking of operations.
- Added functionality to save snippets to the database upon retrieval.
- Updated project overview documentation to reflect new features and structure.
- Refactored existing commands and logic for better modularity and maintainability.

lib/cache/wallets.ts

@@ -0,0 +1,108 @@
+import { NDKCashuWallet, NDKNutzapMonitor } from "@nostr-dev-kit/ndk-wallet";
+import { NDKCashuMintList, NDKPrivateKeySigner, type NDKSigner } from "@nostr-dev-kit/ndk";
+import { ndk } from "../../ndk.js";
+import { log } from "../utils/log.js";
+
+/**
+ * In-memory cache to store NDKCashuWallets by pubkey for efficient retrieval
+ * Used by the zap command to avoid repeatedly fetching wallet events
+ */
+export const walletsCache: Record<string, NDKCashuWallet> = {};
+
+/**
+ * Get a wallet for a pubkey, retrieving from cache if available,
+ * otherwise loading from Nostr
+ * @param pubkey The public key to get the wallet for
+ * @returns The wallet (from cache or newly loaded)
+ */
+export async function getWallet(pubkey: string, signer: NDKSigner): Promise<NDKCashuWallet | undefined> {
+    // Return from cache if available
+    if (walletsCache[pubkey]) {
+        console.log(`Returning cached wallet for ${pubkey}`);
+        return walletsCache[pubkey];
+    }
+
+    ndk.signer = signer;
+    
+    // Not in cache, fetch from Nostr
+    try {
+        let wallet: NDKCashuWallet | undefined;
+        const user = ndk.getUser({pubkey});
+        const event = await ndk.fetchEvent({ kinds: [17375], authors: [pubkey] });
+
+        // Use the existing wallet
+        if (event) {
+            console.log(`Found wallet event for ${pubkey}: ${event.id}`, event.inspect);
+            wallet = await NDKCashuWallet.from(event);
+        } else {
+            console.log('No wallet event found for', pubkey);
+        }
+
+        if (!wallet) {
+            wallet = new NDKCashuWallet(ndk);
+            wallet.mints = ["https://mint.coinos.io"];
+
+            // Generate a P2PK address for receiving nutzaps
+            await wallet.getP2pk();
+            log(`Generated P2PK address for ${pubkey}: ${wallet.p2pk}`);
+            
+            // Publish the wallet info event (kind 17375)
+            await wallet.publish();
+            log(`Published wallet info event for ${pubkey}`);
+            
+            // Set up the mint list for nutzap reception (kind 10019)
+            const mintList = new NDKCashuMintList(ndk);
+            mintList.mints = wallet.mints;
+            mintList.relays = ['wss://relay.pri']
+            mintList.p2pk = wallet.p2pk;
+            
+            // Publish the mint list
+            await mintList.publish();
+            log(`Published mint list for ${pubkey} with mints: ${mintList.mints.join(', ')}`);
+        }
+        
+        
+        // Start wallet for monitoring balance and nutzaps
+        console.log(`Starting wallet for ${pubkey}`);
+        await wallet.start();
+        console.log(`Wallet started for ${pubkey}: ${wallet.balance}`);
+        log(`Started wallet for ${pubkey}: ${wallet.balance}`);
+
+        try {
+            const nutzapMonitor = new NDKNutzapMonitor(ndk, user, {});
+            nutzapMonitor.wallet = wallet;
+            nutzapMonitor.on("seen", () => {
+                log('seen nutzap');
+            });
+            nutzapMonitor.on("redeemed", (events) => {
+                log(`Nutzap redeemed for ${pubkey}: ${events.reduce((acc, event) => acc + event.amount, 0)} sats`);
+            });
+            nutzapMonitor.start({});
+            log(`Started nutzap monitor for ${pubkey}`);
+            
+            // Set up balance update listener
+            wallet.on('balance_updated', (newBalance) => {
+                log(`Balance updated for ${pubkey}: ${newBalance?.amount || 0} sats`);
+            });
+        } catch (error) {
+            console.error(`Error starting nutzap monitor for ${pubkey}:`, error);
+        }
+        
+        walletsCache[pubkey] = wallet;
+        
+        // No wallet found
+        return wallet;
+    } catch (error) {
+        console.error(`Error fetching wallet for ${pubkey}:`, error);
+        return undefined;
+    }
+}
+
+/**
+ * Clear the wallet cache for testing or memory management
+ */
+export function clearWalletsCache(): void {
+    for (const key of Object.keys(walletsCache)) {
+        delete walletsCache[key];
+    }
+}