feat(api): add AccountsController with accounts and cards list endpoints

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

MoneyMap/Controllers/AccountsController.cs

@@ -0,0 +1,65 @@
+using Microsoft.AspNetCore.Mvc;
+using Microsoft.EntityFrameworkCore;
+using MoneyMap.Data;
+
+namespace MoneyMap.Controllers;
+
+[ApiController]
+[Route("api/[controller]")]
+public class AccountsController : ControllerBase
+{
+    private readonly MoneyMapContext _db;
+
+    public AccountsController(MoneyMapContext db) => _db = db;
+
+    [HttpGet]
+    public async Task<IActionResult> List()
+    {
+        var accounts = await _db.Accounts
+            .Include(a => a.Cards)
+            .Include(a => a.Transactions)
+            .OrderBy(a => a.Institution).ThenBy(a => a.Last4)
+            .Select(a => new
+            {
+                a.Id,
+                a.Institution,
+                a.Last4,
+                a.Owner,
+                Label = a.DisplayLabel,
+                TransactionCount = a.Transactions.Count,
+                CardCount = a.Cards.Count
+            })
+            .ToListAsync();
+
+        return Ok(accounts);
+    }
+
+    [HttpGet("cards")]
+    public async Task<IActionResult> ListCards([FromQuery] int? accountId = null)
+    {
+        var q = _db.Cards
+            .Include(c => c.Account)
+            .Include(c => c.Transactions)
+            .AsQueryable();
+
+        if (accountId.HasValue)
+            q = q.Where(c => c.AccountId == accountId.Value);
+
+        var cards = await q
+            .OrderBy(c => c.Owner).ThenBy(c => c.Last4)
+            .Select(c => new
+            {
+                c.Id,
+                c.Issuer,
+                c.Last4,
+                c.Owner,
+                Label = c.DisplayLabel,
+                Account = c.Account != null ? c.Account.Institution + " " + c.Account.Last4 : null,
+                AccountId = c.AccountId,
+                TransactionCount = c.Transactions.Count
+            })
+            .ToListAsync();
+
+        return Ok(cards);
+    }
+}