Phase G: Add Budgeting and Year-End Close

Budgeting:
- Budget + BudgetLine entities with Jan–Dec monthly columns per GL account
- BudgetsController: Index, Create, Edit, SetDefault, Copy, Delete
- Copy action rolls a budget forward to a new fiscal year
- Budget vs. Actual report (BudgetVsActual): compares monthly budget amounts to
  real P&L by calling GetProfitAndLossAsync once per month; variance shown as
  favorable/unfavorable; year + budget selectors in header
- Views: Budgets/Index, Create, Edit with inline annual totals via budget-edit.js
- Nav link + report card on Landing

Year-End Close:
- YearEndClose entity records each closed year + JE reference for audit trail
- AccountsController.YearEndClose GET (history + form) + CloseYear POST
- Close zeroes all Revenue and Expense/COGS account balances into Retained Earnings
  via IAccountBalanceService and posts a supporting JE dated Dec 31
- Idempotency: rejects attempt to close an already-closed year
- Pre-close checklist in view to guide the workflow
- Nav link under Finance

Migration AddBudgetsAndYearEndClose applied

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

src/PowderCoating.Core/Entities/Accounting.cs

@@ -395,3 +395,62 @@ public class FixedAssetDepreciationEntry : BaseEntity
     public virtual FixedAsset FixedAsset { get; set; } = null!;
     public virtual JournalEntry? JournalEntry { get; set; }
 }
+
+/// <summary>
+/// A named annual budget. Contains one BudgetLine per account per month. Supports
+/// multiple budgets per fiscal year (e.g. "Conservative" vs "Optimistic") but only
+/// one is marked IsDefault for the Budget vs. Actual report.
+/// </summary>
+public class Budget : BaseEntity
+{
+    public string Name { get; set; } = string.Empty;
+    public int FiscalYear { get; set; }
+    public string? Notes { get; set; }
+    public bool IsDefault { get; set; } = false;
+
+    public virtual ICollection<BudgetLine> Lines { get; set; } = new List<BudgetLine>();
+}
+
+/// <summary>
+/// Monthly budget amount for one account within a Budget. Jan–Dec stored as separate
+/// columns so the grid editor can write them in a single POST without a line-item loop.
+/// Annual is a computed property summing all twelve months.
+/// </summary>
+public class BudgetLine : BaseEntity
+{
+    public int BudgetId { get; set; }
+    public int AccountId { get; set; }
+
+    public decimal Jan { get; set; }
+    public decimal Feb { get; set; }
+    public decimal Mar { get; set; }
+    public decimal Apr { get; set; }
+    public decimal May { get; set; }
+    public decimal Jun { get; set; }
+    public decimal Jul { get; set; }
+    public decimal Aug { get; set; }
+    public decimal Sep { get; set; }
+    public decimal Oct { get; set; }
+    public decimal Nov { get; set; }
+    public decimal Dec { get; set; }
+
+    public decimal Annual => Jan + Feb + Mar + Apr + May + Jun + Jul + Aug + Sep + Oct + Nov + Dec;
+
+    public virtual Budget Budget { get; set; } = null!;
+    public virtual Account Account { get; set; } = null!;
+}
+
+/// <summary>
+/// Records a completed year-end close. The close posts a JE that zeroes all
+/// Revenue and Expense account balances into Retained Earnings, and marks
+/// the year as closed so it cannot be closed again.
+/// </summary>
+public class YearEndClose : BaseEntity
+{
+    public int ClosedYear { get; set; }
+    public DateTime ClosedAt { get; set; } = DateTime.UtcNow;
+    public string? ClosedBy { get; set; }
+    public int JournalEntryId { get; set; }
+
+    public virtual JournalEntry JournalEntry { get; set; } = null!;
+}