feat(02-01): add chart and month navigation i18n keys

- Add 10 new dashboard keys to en.json (monthNav, noData, charts, etc.)
- Add matching German translations to de.json
- ChartEmptyState component already exists from Phase 1

src/i18n/de.json

@@ -74,7 +74,17 @@
     "overBudget": "über Budget",
     "underBudget": "unter Budget",
     "onTrack": "Im Plan",
-    "loading": "Dashboard wird geladen..."
+    "loading": "Dashboard wird geladen...",
+    "monthNav": "Monat",
+    "noData": "Keine Daten vorhanden",
+    "expenseDonut": "Ausgabenverteilung",
+    "incomeChart": "Einkommen: Budget vs. Ist",
+    "spendChart": "Ausgaben nach Kategorie",
+    "budgeted": "Budgetiert",
+    "actual": "Tatsaechlich",
+    "noBudgetForMonth": "Kein Budget fuer diesen Monat",
+    "createBudget": "Budget erstellen",
+    "generateFromTemplate": "Aus Vorlage generieren"
   },
   "quickAdd": {
     "title": "Schnelleingabe-Bibliothek",

src/i18n/en.json

@@ -74,7 +74,17 @@
     "overBudget": "over budget",
     "underBudget": "under budget",
     "onTrack": "On track",
-    "loading": "Loading dashboard..."
+    "loading": "Loading dashboard...",
+    "monthNav": "Month",
+    "noData": "No data to display",
+    "expenseDonut": "Expense Breakdown",
+    "incomeChart": "Income: Budget vs Actual",
+    "spendChart": "Spending by Category",
+    "budgeted": "Budgeted",
+    "actual": "Actual",
+    "noBudgetForMonth": "No budget for this month",
+    "createBudget": "Create Budget",
+    "generateFromTemplate": "Generate from Template"
   },
   "quickAdd": {
     "title": "Quick Add Library",