Drop cached dinner responses and keep link tokens out of names (PR #97 review F1, F2)

F1: bump the service worker cache version to v2 so activate deletes the
v1 API cache, whose dinner responses still carried the pasted recipe_url
and could be served offline.

F2: nameFromURL now drops words holding a digit and ends the name at the
first credential word (token, access, secret, ...), so a token in the
link's last path segment never reaches the public dinner name.
/recipes/beef-stew is still "Beef stew".

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

internal/dinners/dinners_test.go

@@ -19,6 +19,13 @@ func TestNameFromURL(t *testing.T) {
 		{"https://example.com/", ""},
 		{"https://example.com/recipe/98765", ""},
 		{"https://example.com/the-best-easy-recipe", ""},
+		{"https://example.com/best-chili-v2", "Best chili"},
+		{"https://example.com/stew-access_token-personaltokenabc123", "Stew"},
+		{"https://example.com/stew-token-abcdefghijk", "Stew"},
+		{"https://example.com/chili-api-key-zyxwvut", "Chili"},
+		{"https://example.com/stew-x7k2p9q4", "Stew"},
+		{"https://example.com/recipes/token-abcdefghijk", ""},
+		{"https://example.com/key-lime-pie", "Key lime pie"},
 	}
 	for _, tt := range tests {
 		u, err := url.Parse(tt.link)