Add budget module and push notifications for transactions

Budget: recurring items CRUD, yearly/monthly projections with no-double-count
logic, and full UI (overview, monthly detail, recurring items manager).

Push notifications: Web Push via VAPID keys, triggered on transaction creation
from n8n. Includes service worker handlers, frontend subscription flow, and
a test button on the Dashboard (temporary).

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

backend/app/models/models.py

@@ -2,11 +2,24 @@ import enum
 from datetime import datetime
 from typing import Optional
 
-from sqlalchemy import Column
-from sqlalchemy.dialects.postgresql import JSONB
+from sqlalchemy import JSON, Column
 from sqlmodel import Field, Relationship, SQLModel
 
 
+class RecurringItemType(str, enum.Enum):
+    INCOME = "INCOME"
+    EXPENSE = "EXPENSE"
+    SAVINGS = "SAVINGS"
+
+
+class RecurringFrequency(str, enum.Enum):
+    WEEKLY = "WEEKLY"
+    MONTHLY = "MONTHLY"
+    QUARTERLY = "QUARTERLY"
+    BIANNUAL = "BIANNUAL"
+    YEARLY = "YEARLY"
+
+
 class TransactionType(str, enum.Enum):
     COMPRA = "COMPRA"
     DEVOLUCION = "DEVOLUCION"
@@ -207,7 +220,7 @@ class UserSettings(SQLModel, table=True):
     key: str = Field(index=True, unique=True, default="default")
     data: dict = Field(
         default_factory=dict,
-        sa_column=Column(JSONB, nullable=False, server_default="{}"),
+        sa_column=Column(JSON, nullable=False, server_default="{}"),
     )
     updated_at: datetime = Field(default_factory=datetime.utcnow)
 
@@ -220,3 +233,69 @@ class UserSettingsRead(SQLModel):
 
 class UserSettingsUpdate(SQLModel):
     data: dict
+
+
+# --- Recurring Item ---
+
+
+class RecurringItemBase(SQLModel):
+    name: str
+    amount: float
+    currency: Currency = Currency.CRC
+    item_type: RecurringItemType
+    frequency: RecurringFrequency = RecurringFrequency.MONTHLY
+    day_of_month: Optional[int] = None
+    month_of_year: Optional[int] = None
+    override_amounts: Optional[dict] = Field(
+        default=None,
+        sa_column=Column(JSON, nullable=True),
+    )
+    category_id: Optional[int] = Field(default=None, foreign_key="category.id")
+    is_active: bool = True
+    notes: Optional[str] = None
+
+
+class RecurringItem(RecurringItemBase, table=True):
+    id: Optional[int] = Field(default=None, primary_key=True)
+    created_at: datetime = Field(default_factory=datetime.utcnow)
+    category: Optional[Category] = Relationship()
+
+
+class RecurringItemCreate(RecurringItemBase):
+    pass
+
+
+class RecurringItemRead(RecurringItemBase):
+    id: int
+    created_at: datetime
+    category: Optional[CategoryRead] = None
+
+
+class RecurringItemUpdate(SQLModel):
+    name: Optional[str] = None
+    amount: Optional[float] = None
+    currency: Optional[Currency] = None
+    item_type: Optional[RecurringItemType] = None
+    frequency: Optional[RecurringFrequency] = None
+    day_of_month: Optional[int] = None
+    month_of_year: Optional[int] = None
+    override_amounts: Optional[dict] = None
+    category_id: Optional[int] = None
+    is_active: Optional[bool] = None
+    notes: Optional[str] = None
+
+
+# --- Push Subscription ---
+
+
+class PushSubscription(SQLModel, table=True):
+    id: Optional[int] = Field(default=None, primary_key=True)
+    endpoint: str = Field(unique=True)
+    p256dh: str
+    auth: str
+    created_at: datetime = Field(default_factory=datetime.utcnow)
+
+
+class PushSubscriptionCreate(SQLModel):
+    endpoint: str
+    keys: dict  # {"p256dh": "...", "auth": "..."}