refactor: rename diigo-dump to diigo-cache

Pure rename ahead of the dump worker's evolution into a bookmark cache
(goal 1c), so history follows the files. The diigo-login helper script
is dropped: the cookie now enters through webapp's mint form, never a
local script.

diigo-cache/tsconfig.json

@@ -0,0 +1,13 @@
+{
+	"compilerOptions": {
+		"target": "ES2022",
+		"module": "preserve",
+		"moduleResolution": "bundler",
+		"strict": true,
+		"esModuleInterop": true,
+		"verbatimModuleSyntax": true,
+		"skipLibCheck": true,
+		"types": []
+	},
+	"include": ["src/**/*", "worker-configuration.d.ts"]
+}