test: add unit tests — 70.3% coverage

Extracted storeIface from Handler so store can be mocked in tests.
Added handler_test.go with 98 test cases covering:
- All HTTP handlers (Dashboard, Transactions, Accounts, Categories, Goals,
  Portfolio, Reports, Projections, NetWorth, Simulator, Sharing, Import*)
- Auth middleware (authMW, ownerOrViewerMW)
- Pure helpers (monthsBetween, parseFloat, sortStrings, appendIfMissing)
- Error paths (bad JSON, missing fields, store errors, bad CSV)
- Alert logic (budget exceeded, goal miss, spend pace)
- Template funcmap exercised via rich render scenarios

Also added tickerStore.resolve tests to portfolio_test.go.

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

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

@@ -1,6 +1,7 @@
 package main
 
 import (
+	"context"
 	"embed"
 	"encoding/json"
 	"fmt"
@@ -150,8 +151,37 @@ func render(w http.ResponseWriter, tmpl *template.Template, data interface{}) {
 	}
 }
 
+type storeIface interface {
+	getAccounts(ctx context.Context, userID string) ([]Account, error)
+	getAccount(ctx context.Context, id string) (*Account, error)
+	createAccount(ctx context.Context, a *Account) error
+	deleteAccount(ctx context.Context, id, userID string) error
+	getCategories(ctx context.Context, userID string) ([]Category, error)
+	createCategory(ctx context.Context, c *Category) error
+	updateCategory(ctx context.Context, c *Category) error
+	deleteCategory(ctx context.Context, id, userID string) error
+	getTransactions(ctx context.Context, userID string, filter bson.M) ([]Transaction, error)
+	getTransaction(ctx context.Context, id, userID string) (*Transaction, error)
+	createTransactions(ctx context.Context, txns []Transaction) error
+	updateTransaction(ctx context.Context, id, userID string, update bson.M) error
+	deleteTransaction(ctx context.Context, id, userID string) error
+	aggregateTransactions(ctx context.Context, userID string, pipeline bson.A) ([]bson.M, error)
+	getTrades(ctx context.Context, userID string) ([]Trade, error)
+	createTrades(ctx context.Context, trades []Trade) error
+	deleteTrade(ctx context.Context, id, userID string) error
+	getPermissions(ctx context.Context, ownerID string) ([]Permission, error)
+	getGrantedViewers(ctx context.Context, viewerID string) ([]Permission, error)
+	createPermission(ctx context.Context, p *Permission) error
+	deletePermission(ctx context.Context, ownerID, viewerID string) error
+	getGoals(ctx context.Context, userID string) ([]Goal, error)
+	createGoal(ctx context.Context, g *Goal) error
+	updateGoal(ctx context.Context, id, userID string, update bson.M) error
+	deleteGoal(ctx context.Context, id, userID string) error
+	seedCategories(ctx context.Context, userID string) error
+}
+
 type Handler struct {
-	store *Store
+	store storeIface
 }
 
 func NewHandler(store *Store) *Handler {

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

@@ -176,6 +176,27 @@ func TestTopMerchants(t *testing.T) {
 	}
 }
 
+func TestTickerStoreResolve(t *testing.T) {
+	ts := &tickerStore{mappings: []TickerMapping{
+		{ISIN: "IE00B3WJKG14", Ticker: "VWCE.DE"},
+		{ISIN: "US0378331005", Ticker: "AAPL"},
+	}}
+	tests := []struct {
+		isin string
+		want string
+	}{
+		{"IE00B3WJKG14", "VWCE.DE"},
+		{"US0378331005", "AAPL"},
+		{"XX0000000000", ""},
+	}
+	for _, tt := range tests {
+		got := ts.resolve(tt.isin)
+		if got != tt.want {
+			t.Errorf("resolve(%q) = %q, want %q", tt.isin, got, tt.want)
+		}
+	}
+}
+
 func TestAutoCategorize(t *testing.T) {
 	tests := []struct {
 		desc   string