enhance: thread-safe CookieJar, SameSite cookie attr, dynamic Google countries

- Wrap staticCookieJar in struct with sync.RWMutex for thread safety
- Add SameSite field to Cookie struct with Strict/Lax/None constants
- Update Playwright cookie conversion functions for SameSite
- Replace hardcoded 4-country switch with dynamic country code generation

Closes #20, #22, #23
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

sites/google/google.go

@@ -5,6 +5,7 @@ import (
 	"fmt"
 	"log/slog"
 	"net/url"
+	"strings"
 
 	"gitea.stevedudenhoeffer.com/steve/go-extractor"
 )
@@ -65,24 +66,7 @@ func (c Config) Search(ctx context.Context, b extractor.Browser, query string) (
 	}
 
 	if c.Country != "" {
-		country := ""
-		switch c.Country {
-		case "us":
-			country = "countryUS"
-
-		case "uk":
-			country = "countryUK"
-
-		case "au":
-			country = "countryAU"
-
-		case "ca":
-			country = "countryCA"
-		}
-
-		if country != "" {
-			vals.Set("cr", country)
-		}
+		vals.Set("cr", "country"+strings.ToUpper(c.Country))
 	}
 
 	u.RawQuery = vals.Encode()