feat: phase 6 — dashboard alerts and nudges

Adds server-computed alert banners to the dashboard:
- Budget exceeded (red): when a category spend is over 100% of budget
- Budget pace warning (amber): 80%+ of budget used but <80% of month elapsed
- Goal deadline risk (amber): avg savings rate too low to hit a goal on time
- Spend pace warning (amber): disposable spending is 20%+ ahead of month progress

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

apps/finance/services/api/main/handler.go

@@ -438,6 +438,81 @@ func (h *Handler) Dashboard(w http.ResponseWriter, r *http.Request) {
 		}
 	}
 
+	// ── Alerts ──────────────────────────────────────────────────────────
+	var alerts []Alert
+
+	// budget overspend alerts — compare per-category spend vs budget
+	for cat, budget := range catBudgets {
+		spent := -thisMonth.ByCategory[cat] // expenses are negative
+		if spent <= 0 || budget <= 0 {
+			continue
+		}
+		pct := int(float64(spent) / float64(budget) * 100)
+		if pct >= 100 {
+			alerts = append(alerts, Alert{
+				Level:   AlertDanger,
+				Message: fmt.Sprintf("You've exceeded your %s budget (€%.0f of €%.0f — %d%%).", cat, float64(spent)/100, float64(budget)/100, pct),
+			})
+		} else if pct >= 80 && monthProgressPct < 80 {
+			alerts = append(alerts, Alert{
+				Level:   AlertWarn,
+				Message: fmt.Sprintf("You've used %d%% of your %s budget but only %d%% of the month has passed.", pct, cat, monthProgressPct),
+			})
+		}
+	}
+
+	// goal deadline risk alerts
+	if goalList, err := h.store.getGoals(ctx, a.UserID); err == nil {
+		threeAgo := time.Date(now.Year(), now.Month(), 1, 0, 0, 0, 0, now.Location()).AddDate(0, -3, 0)
+		moSavings := make(map[int]int64)
+		for _, t := range txns {
+			if !t.Date.Before(threeAgo) && t.Date.Before(thisStart) {
+				moSavings[int(t.Date.Month())] += t.AmountCents
+			}
+		}
+		var totalS int64
+		for _, s := range moSavings {
+			if s > 0 {
+				totalS += s
+			}
+		}
+		avgS := int64(0)
+		if len(moSavings) > 0 {
+			avgS = totalS / int64(len(moSavings))
+		}
+		for _, g := range goalList {
+			remaining := g.TargetCents - g.SavedCents
+			if remaining <= 0 {
+				continue
+			}
+			ml := int64(monthsBetween(now, g.Deadline))
+			if ml < 1 {
+				ml = 1
+			}
+			needed := remaining / ml
+			if avgS < needed {
+				monthsOff := int64(0)
+				if avgS > 0 {
+					monthsOff = remaining/avgS - ml
+				}
+				msg := fmt.Sprintf("You're on track to miss your \"%s\" goal", g.Name)
+				if monthsOff > 0 {
+					msg += fmt.Sprintf(" by %d month(s)", monthsOff)
+				}
+				msg += fmt.Sprintf(" — need €%.0f/mo but saving ~€%.0f/mo.", float64(needed)/100, float64(avgS)/100)
+				alerts = append(alerts, Alert{Level: AlertWarn, Message: msg})
+			}
+		}
+	}
+
+	// overall spend pace alert
+	if monthProgressPct > 0 && monthSpentPct > monthProgressPct+20 {
+		alerts = append(alerts, Alert{
+			Level:   AlertWarn,
+			Message: fmt.Sprintf("You've spent %d%% of your disposable income but only %d%% of the month has passed — you're ahead of pace.", monthSpentPct, monthProgressPct),
+		})
+	}
+
 	render(w, dashboardTmpl, &DashboardData{
 		UserID:                  a.UserID,
 		Email:                   a.Email,
@@ -467,6 +542,7 @@ func (h *Handler) Dashboard(w http.ResponseWriter, r *http.Request) {
 		PortfolioHoldings:            portfolioHoldings,
 		PortfolioPricesAvailable:     portfolioPricesAvailable,
 		NetWorthCents:                portfolioValueCents + running,
+		Alerts:                       alerts,
 	})
 }
 

apps/finance/services/api/main/models.go

@@ -154,6 +154,8 @@ type DashboardData struct {
 	PortfolioPricesAvailable bool
 
 	NetWorthCents int64
+
+	Alerts []Alert
 }
 
 type PeriodSummary struct {
@@ -219,6 +221,19 @@ type SharingUser struct {
 	Email string
 }
 
+type AlertLevel string
+
+const (
+	AlertWarn  AlertLevel = "warn"
+	AlertDanger AlertLevel = "danger"
+	AlertInfo  AlertLevel = "info"
+)
+
+type Alert struct {
+	Level   AlertLevel
+	Message string
+}
+
 type SimulatorGoal struct {
 	Name         string
 	MonthlyCents int64

apps/finance/services/api/main/templates/dashboard.html

@@ -6,6 +6,20 @@
   <span class="text-muted">{{if $d.Email}}{{$d.Email}}{{end}}</span>
 </div>
 
+{{if $d.Alerts}}
+<div style="display:flex; flex-direction:column; gap:8px; margin-bottom:16px;">
+  {{range $d.Alerts}}
+  <div style="display:flex; align-items:flex-start; gap:10px; padding:12px 16px; border-radius:10px; font-size:13px;
+       {{if eq .Level "danger"}}background:rgba(248,113,113,0.08); border:1px solid rgba(248,113,113,0.25); color:var(--red);
+       {{else if eq .Level "warn"}}background:rgba(245,158,11,0.08); border:1px solid rgba(245,158,11,0.25); color:#f59e0b;
+       {{else}}background:rgba(105,121,248,0.08); border:1px solid rgba(105,121,248,0.25); color:var(--accent);{{end}}">
+    <span style="flex-shrink:0; font-size:15px;">{{if eq .Level "danger"}}🔴{{else if eq .Level "warn"}}⚠{{else}}ℹ{{end}}</span>
+    <span>{{.Message}}</span>
+  </div>
+  {{end}}
+</div>
+{{end}}
+
 <!-- HERO: available to spend -->
 <div class="card animate-on-scroll" style="margin-bottom:16px; padding:24px 28px;">
   <div style="font-size:12px; color:var(--text2); text-transform:uppercase; letter-spacing:.5px; margin-bottom:10px; display:flex; align-items:center; gap:8px;">