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
+}