feature: add CoinGecko cryptocurrency price extractor

Add sites/coingecko package with GetPrice() method that extracts
structured crypto price data (name, symbol, price, 24h/7d change,
market cap, volume, 24h high/low) from CoinGecko coin pages.

Includes mock-based tests and parseLargeNumber helper for T/B/M suffixes.

Closes #27

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

sites/coingecko/coingecko_test.go

@@ -0,0 +1,198 @@
+package coingecko
+
+import (
+	"context"
+	"testing"
+
+	"gitea.stevedudenhoeffer.com/steve/go-extractor"
+	"gitea.stevedudenhoeffer.com/steve/go-extractor/extractortest"
+)
+
+func makeBitcoinDoc() *extractortest.MockDocument {
+	return &extractortest.MockDocument{
+		URLValue: "https://www.coingecko.com/en/coins/bitcoin",
+		MockNode: extractortest.MockNode{
+			Children: map[string]extractor.Nodes{
+				"div[data-coin-show-target='coin'] h1": {
+					&extractortest.MockNode{TextValue: "Bitcoin"},
+				},
+				"span[data-coin-symbol]": {
+					&extractortest.MockNode{TextValue: "btc"},
+				},
+				"span[data-converter-target='price']": {
+					&extractortest.MockNode{TextValue: "$97,234.56"},
+				},
+				"span[data-price-change='24h']": {
+					&extractortest.MockNode{TextValue: "-2.34%"},
+				},
+				"span[data-price-change='7d']": {
+					&extractortest.MockNode{TextValue: "5.67%"},
+				},
+				"span[data-coin-stat='market-cap']": {
+					&extractortest.MockNode{TextValue: "$1.92T"},
+				},
+				"span[data-coin-stat='volume']": {
+					&extractortest.MockNode{TextValue: "$28.5B"},
+				},
+				"span[data-coin-stat='high-24h']": {
+					&extractortest.MockNode{TextValue: "$98,100.00"},
+				},
+				"span[data-coin-stat='low-24h']": {
+					&extractortest.MockNode{TextValue: "$95,500.00"},
+				},
+			},
+		},
+	}
+}
+
+func TestExtractCoinPrice(t *testing.T) {
+	doc := makeBitcoinDoc()
+
+	data, err := extractCoinPrice(doc)
+	if err != nil {
+		t.Fatalf("extractCoinPrice() error: %v", err)
+	}
+
+	if data.Name != "Bitcoin" {
+		t.Errorf("Name = %q, want %q", data.Name, "Bitcoin")
+	}
+	if data.Symbol != "BTC" {
+		t.Errorf("Symbol = %q, want %q", data.Symbol, "BTC")
+	}
+	if data.Price != 97234.56 {
+		t.Errorf("Price = %v, want 97234.56", data.Price)
+	}
+	if data.Change24h != -2.34 {
+		t.Errorf("Change24h = %v, want -2.34", data.Change24h)
+	}
+	if data.Change7d != 5.67 {
+		t.Errorf("Change7d = %v, want 5.67", data.Change7d)
+	}
+	if data.MarketCap != 1_920_000_000_000 {
+		t.Errorf("MarketCap = %v, want 1920000000000", data.MarketCap)
+	}
+	if data.Volume24h != 28_500_000_000 {
+		t.Errorf("Volume24h = %v, want 28500000000", data.Volume24h)
+	}
+	if data.High24h != 98100.00 {
+		t.Errorf("High24h = %v, want 98100.00", data.High24h)
+	}
+	if data.Low24h != 95500.00 {
+		t.Errorf("Low24h = %v, want 95500.00", data.Low24h)
+	}
+}
+
+func TestExtractCoinPrice_NameFallback(t *testing.T) {
+	doc := &extractortest.MockDocument{
+		MockNode: extractortest.MockNode{
+			Children: map[string]extractor.Nodes{
+				"h1": {
+					&extractortest.MockNode{TextValue: "Ethereum"},
+				},
+				"span[data-converter-target='price']": {
+					&extractortest.MockNode{TextValue: "$3,456.78"},
+				},
+			},
+		},
+	}
+
+	data, err := extractCoinPrice(doc)
+	if err != nil {
+		t.Fatalf("extractCoinPrice() error: %v", err)
+	}
+
+	if data.Name != "Ethereum" {
+		t.Errorf("Name = %q, want %q", data.Name, "Ethereum")
+	}
+	if data.Price != 3456.78 {
+		t.Errorf("Price = %v, want 3456.78", data.Price)
+	}
+}
+
+func TestExtractCoinPrice_PriceFallback(t *testing.T) {
+	doc := &extractortest.MockDocument{
+		MockNode: extractortest.MockNode{
+			Children: map[string]extractor.Nodes{
+				"span[data-price-target='price']": {
+					&extractortest.MockNode{TextValue: "$0.5432"},
+				},
+			},
+		},
+	}
+
+	data, err := extractCoinPrice(doc)
+	if err != nil {
+		t.Fatalf("extractCoinPrice() error: %v", err)
+	}
+
+	if data.Price != 0.5432 {
+		t.Errorf("Price = %v, want 0.5432", data.Price)
+	}
+}
+
+func TestExtractCoinPrice_Empty(t *testing.T) {
+	doc := &extractortest.MockDocument{
+		MockNode: extractortest.MockNode{
+			Children: map[string]extractor.Nodes{},
+		},
+	}
+
+	data, err := extractCoinPrice(doc)
+	if err != nil {
+		t.Fatalf("extractCoinPrice() error: %v", err)
+	}
+
+	if data.Name != "" || data.Price != 0 {
+		t.Error("expected zero values for empty doc")
+	}
+}
+
+func TestGetPrice_MockBrowser(t *testing.T) {
+	doc := makeBitcoinDoc()
+
+	browser := &extractortest.MockBrowser{
+		Documents: map[string]*extractortest.MockDocument{
+			"https://www.coingecko.com/en/coins/bitcoin": doc,
+		},
+	}
+
+	data, err := DefaultConfig.GetPrice(context.Background(), browser, "bitcoin")
+	if err != nil {
+		t.Fatalf("GetPrice() error: %v", err)
+	}
+
+	if data.Name != "Bitcoin" {
+		t.Errorf("Name = %q, want %q", data.Name, "Bitcoin")
+	}
+	if data.Price != 97234.56 {
+		t.Errorf("Price = %v, want 97234.56", data.Price)
+	}
+}
+
+func TestParseLargeNumber(t *testing.T) {
+	tests := []struct {
+		input string
+		want  float64
+	}{
+		{"$1.92T", 1_920_000_000_000},
+		{"$28.5B", 28_500_000_000},
+		{"$250M", 250_000_000},
+		{"$1,234,567", 1234567},
+		{"$0.50", 0.50},
+	}
+
+	for _, tt := range tests {
+		got := parseLargeNumber(tt.input)
+		if got != tt.want {
+			t.Errorf("parseLargeNumber(%q) = %v, want %v", tt.input, got, tt.want)
+		}
+	}
+}
+
+func TestCoinURL(t *testing.T) {
+	got := coinURL("Bitcoin")
+	want := "https://www.coingecko.com/en/coins/bitcoin"
+	if got != want {
+		t.Errorf("coinURL(\"Bitcoin\") = %q, want %q", got, want)
+	}
+}