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.

logic/wallet-balance.ts

@@ -0,0 +1,87 @@
+import { z } from "zod";
+import { getUser } from "../config.js";
+import { getWallet } from "../lib/cache/wallets.js";
+import { getSigner } from "../lib/nostr/utils.js";
+import { log } from "../lib/utils/log.js";
+import { ndk } from "../ndk.js";
+import type { McpServer } from "@modelcontextprotocol/sdk/server/mcp.js";
+
+/**
+ * Get the balance for a user's wallet
+ * @param username Username to check balance for
+ * @returns Balance information
+ */
+export async function getWalletBalance(username: string): Promise<{
+    balance: number;
+    mint_balances: Record<string, number>;
+    message: string;
+}> {
+    try {
+        // Get the appropriate signer based on username
+        const signer = await getSigner(username);
+        
+        // Set the signer for this operation
+        ndk.signer = signer;
+
+        const user = await signer.user();
+        const pubkey = user.pubkey;
+        
+        // Get wallet for the pubkey
+        const wallet = await getWallet(pubkey, signer);
+        if (!wallet) {
+            throw new Error(`No wallet found for ${username}`);
+        }
+        
+        // Get wallet balance
+        const totalBalance = wallet.balance?.amount || 0;
+        log(`Wallet balance for ${username}: ${totalBalance} sats`);
+        
+        // Get individual mint balances
+        const mintBalances: Record<string, number> = {};
+        for (const [mintUrl, balance] of Object.entries(wallet.mintBalances)) {
+            mintBalances[mintUrl] = balance;
+            log(`  - ${mintUrl}: ${balance} sats`);
+        }
+        
+        return {
+            balance: totalBalance,
+            mint_balances: mintBalances,
+            message: `Wallet balance for ${username}: ${totalBalance} sats`,
+        };
+    } catch (error: unknown) {
+        const errorMessage = 
+            error instanceof Error ? error.message : String(error);
+        throw new Error(`Failed to get wallet balance: ${errorMessage}`);
+    }
+}
+
+/**
+ * Add the wallet-balance command to the MCP server
+ * @param server MCP server to add the command to
+ */
+export function addWalletBalanceCommand(server: McpServer) {
+    server.tool(
+        "wallet_balance",
+        "Get the balance of a user's wallet",
+        {
+            username: z.string().describe("Username to check balance for"),
+        },
+        async ({ username }) => {
+            const result = await getWalletBalance(username);
+            
+            return {
+                content: [
+                    {
+                        type: "text",
+                        text: result.message,
+                    },
+                ],
+                // Include detailed balance information in the response
+                wallet_balance: {
+                    total: result.balance,
+                    mints: result.mint_balances,
+                },
+            };
+        }
+    );
+}