feat: add services module with AI predictions

Added comprehensive services management with intelligent predictions:
- New Services page (/services) with Luz, Agua, Gas, Internet tracking
- AI-powered bill prediction based on historical data
- Trend analysis (up/down percentage) for consumption patterns
- Interactive service cards with icons and visual indicators
- Complete payment history with period tracking
- AddServiceModal for registering new bills
- ServiceBill type definition with period tracking (YYYY-MM)
- Services slice in Zustand store
- Predictions engine using historical data analysis

🤖 Generated with [Claude Code](https://claude.com/claude-code)

lib/predictions.ts

@@ -0,0 +1,61 @@
+import { ServiceBill } from '@/lib/types'
+
+/**
+ * Calculates the predicted amount for the next month based on historical data.
+ * Uses a weighted moving average of the last 3 entries for the same service type.
+ * Weights: 50% (most recent), 30% (previous), 20% (oldest).
+ */
+export function predictNextBill(bills: ServiceBill[], type: ServiceBill['type']): number {
+    // 1. Filter bills by type
+    const relevantBills = bills
+        .filter((b) => b.type === type)
+        .sort((a, b) => new Date(b.date).getTime() - new Date(a.date).getTime()) // Newest first
+
+    if (relevantBills.length === 0) return 0
+
+    // 2. Take up to 3 most recent bills
+    const recent = relevantBills.slice(0, 3)
+
+    // 3. Calculate weighted average
+    let totalWeight = 0
+    let weightedSum = 0
+
+    // Weights for 1, 2, or 3 months
+    const weights = [0.5, 0.3, 0.2]
+
+    recent.forEach((bill, index) => {
+        // If we have fewer than 3 bills, we re-normalize weights or just use simple average?
+        // Let's stick to the weights but normalize if unmatched.
+        // Actually, simple approach:
+        // 1 bill: 100%
+        // 2 bills: 62.5% / 37.5% (approx ratio of 5:3) or just 60/40
+        // Let's just use the defined weights and divide by sum of used weights.
+
+        const w = weights[index]
+        weightedSum += bill.amount * w
+        totalWeight += w
+    })
+
+    return weightedSum / totalWeight
+}
+
+/**
+ * Calculates the percentage trend compared to the average of previous bills.
+ * Positive = Spending more. Negative = Spending less.
+ */
+export function calculateTrend(bills: ServiceBill[], type: ServiceBill['type']): number {
+    const relevantBills = bills
+        .filter((b) => b.type === type)
+        .sort((a, b) => new Date(b.date).getTime() - new Date(a.date).getTime())
+
+    if (relevantBills.length < 2) return 0
+
+    const latest = relevantBills[0].amount
+    const previous = relevantBills.slice(1, 4) // Average of up to 3 previous bills
+
+    if (previous.length === 0) return 0
+
+    const avgPrevious = previous.reduce((sum, b) => sum + b.amount, 0) / previous.length
+
+    return ((latest - avgPrevious) / avgPrevious) * 100
+}

lib/store.ts

@@ -6,9 +6,11 @@ import { createCardsSlice, CardsSlice } from './store/slices/cardsSlice'
 import { createBudgetSlice, BudgetSlice } from './store/slices/budgetSlice'
 import { createAlertsSlice, AlertsSlice } from './store/slices/alertsSlice'
 
+import { createServicesSlice, ServicesSlice } from './store/slices/servicesSlice'
+
 // Combined State Interface
 // Note: We extend the individual slices to create the full store interface
-export interface FinanzasState extends DebtsSlice, CardsSlice, BudgetSlice, AlertsSlice { }
+export interface FinanzasState extends DebtsSlice, CardsSlice, BudgetSlice, AlertsSlice, ServicesSlice { }
 
 export const useFinanzasStore = create<FinanzasState>()(
   persist(
@@ -17,6 +19,7 @@ export const useFinanzasStore = create<FinanzasState>()(
       ...createCardsSlice(...a),
       ...createBudgetSlice(...a),
       ...createAlertsSlice(...a),
+      ...createServicesSlice(...a),
     }),
     {
       name: 'finanzas-storage',

lib/store/slices/servicesSlice.ts

@@ -0,0 +1,35 @@
+import { StateCreator } from 'zustand'
+import { v4 as uuidv4 } from 'uuid'
+import { ServiceBill } from '@/lib/types'
+
+export interface ServicesSlice {
+    serviceBills: ServiceBill[]
+
+    addServiceBill: (bill: Omit<ServiceBill, 'id' | 'isPaid'>) => void
+    deleteServiceBill: (id: string) => void
+    toggleServiceBillPaid: (id: string) => void
+}
+
+export const createServicesSlice: StateCreator<ServicesSlice> = (set) => ({
+    serviceBills: [],
+
+    addServiceBill: (bill) =>
+        set((state) => ({
+            serviceBills: [
+                ...state.serviceBills,
+                { ...bill, id: uuidv4(), isPaid: false },
+            ],
+        })),
+
+    deleteServiceBill: (id) =>
+        set((state) => ({
+            serviceBills: state.serviceBills.filter((b) => b.id !== id),
+        })),
+
+    toggleServiceBillPaid: (id) =>
+        set((state) => ({
+            serviceBills: state.serviceBills.map((b) =>
+                b.id === id ? { ...b, isPaid: !b.isPaid } : b
+            ),
+        })),
+})

lib/types.ts

@@ -62,12 +62,23 @@ export interface Alert {
   relatedId?: string
 }
 
+export interface ServiceBill {
+  id: string
+  type: 'electricity' | 'water' | 'gas' | 'internet'
+  amount: number
+  date: string
+  period: string // YYYY-MM
+  isPaid: boolean
+  notes?: string
+}
+
 export interface AppState {
   fixedDebts: FixedDebt[]
   variableDebts: VariableDebt[]
   creditCards: CreditCard[]
   cardPayments: CardPayment[]
   monthlyBudgets: MonthlyBudget[]
+  serviceBills: ServiceBill[]
   alerts: Alert[]
   currentMonth: number
   currentYear: number