feat(frontend): add API client, layout, and routing

- Create Axios-based API client with sources, jobs, and dashboard endpoints
- Add responsive Layout component with navigation sidebar
- Set up React Router with Dashboard, Backups, and Settings routes
- Configure TanStack Query provider with default options
- Use lucide-react for navigation icons

frontend/node_modules/rrweb-cssom/lib/CSSConditionRule.js

@@ -0,0 +1,25 @@
+//.CommonJS
+var CSSOM = {
+  CSSRule: require("./CSSRule").CSSRule,
+  CSSGroupingRule: require("./CSSGroupingRule").CSSGroupingRule
+};
+///CommonJS
+
+
+/**
+ * @constructor
+ * @see https://www.w3.org/TR/css-conditional-3/#the-cssconditionrule-interface
+ */
+CSSOM.CSSConditionRule = function CSSConditionRule() {
+  CSSOM.CSSGroupingRule.call(this);
+  this.cssRules = [];
+};
+
+CSSOM.CSSConditionRule.prototype = new CSSOM.CSSGroupingRule();
+CSSOM.CSSConditionRule.prototype.constructor = CSSOM.CSSConditionRule;
+CSSOM.CSSConditionRule.prototype.conditionText = ''
+CSSOM.CSSConditionRule.prototype.cssText = ''
+
+//.CommonJS
+exports.CSSConditionRule = CSSOM.CSSConditionRule;
+///CommonJS