Initial commit: MyMidas personal finance tracker

Full-stack self-hosted finance app with FastAPI backend and React frontend.

Features:
- Accounts, transactions, budgets, investments with GBP base currency
- CSV import with auto-detection for 10 UK bank formats
- ML predictions: spending forecast, net worth projection, Monte Carlo
- 7 selectable themes (Obsidian, Arctic, Midnight, Vault, Terminal, Synthwave, Ledger)
- Receipt/document attachments on transactions (JPEG, PNG, WebP, PDF)
- AES-256-GCM field encryption, RS256 JWT, TOTP 2FA, RLS, audit log
- Encrypted nightly backups + key rotation script
- Mobile-responsive layout with bottom nav

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

backend/app/schemas/budget.py

@@ -0,0 +1,65 @@
+import uuid
+from datetime import date as DateType, datetime
+from decimal import Decimal
+from typing import Literal
+
+from pydantic import BaseModel, Field
+
+BudgetPeriod = Literal["weekly", "monthly", "quarterly", "yearly"]
+
+
+class BudgetCreate(BaseModel):
+    category_id: uuid.UUID
+    name: str = Field(..., min_length=1, max_length=200)
+    amount: Decimal = Field(..., gt=0)
+    currency: str = Field(default="GBP", min_length=3, max_length=10)
+    period: BudgetPeriod = "monthly"
+    start_date: DateType
+    end_date: DateType | None = None
+    rollover: bool = False
+    alert_threshold: Decimal = Field(default=Decimal("80"), ge=0, le=100)
+
+
+class BudgetUpdate(BaseModel):
+    name: str | None = Field(default=None, min_length=1, max_length=200)
+    amount: Decimal | None = Field(default=None, gt=0)
+    period: BudgetPeriod | None = None
+    end_date: DateType | None = None
+    rollover: bool | None = None
+    alert_threshold: Decimal | None = Field(default=None, ge=0, le=100)
+    is_active: bool | None = None
+
+
+class BudgetResponse(BaseModel):
+    id: uuid.UUID
+    category_id: uuid.UUID
+    name: str
+    amount: Decimal
+    currency: str
+    period: str
+    start_date: DateType
+    end_date: DateType | None
+    rollover: bool
+    alert_threshold: Decimal
+    is_active: bool
+    created_at: datetime
+    updated_at: datetime
+
+    model_config = {"from_attributes": True}
+
+
+class BudgetSummaryItem(BaseModel):
+    budget_id: uuid.UUID
+    budget_name: str
+    category_id: uuid.UUID
+    category_name: str
+    period: str
+    budget_amount: Decimal
+    spent_amount: Decimal
+    remaining_amount: Decimal
+    percent_used: Decimal
+    is_over_budget: bool
+    alert_triggered: bool
+    currency: str
+    period_start: DateType
+    period_end: DateType