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/tailwindcss/lib/util/applyImportantSelector.js

@@ -0,0 +1,38 @@
+"use strict";
+Object.defineProperty(exports, "__esModule", {
+    value: true
+});
+Object.defineProperty(exports, "applyImportantSelector", {
+    enumerable: true,
+    get: function() {
+        return applyImportantSelector;
+    }
+});
+const _postcssselectorparser = /*#__PURE__*/ _interop_require_default(require("postcss-selector-parser"));
+const _pseudoElements = require("./pseudoElements");
+function _interop_require_default(obj) {
+    return obj && obj.__esModule ? obj : {
+        default: obj
+    };
+}
+function applyImportantSelector(selector, important) {
+    let sel = (0, _postcssselectorparser.default)().astSync(selector);
+    sel.each((sel)=>{
+        // For nesting, we only need to wrap a selector with :is() if it has a top-level combinator,
+        // e.g. `.dark .text-white`, to be independent of DOM order. Any other selector, including
+        // combinators inside of pseudos like `:where()`, are ok to nest.
+        let shouldWrap = sel.nodes.some((node)=>node.type === "combinator");
+        if (shouldWrap) {
+            sel.nodes = [
+                _postcssselectorparser.default.pseudo({
+                    value: ":is",
+                    nodes: [
+                        sel.clone()
+                    ]
+                })
+            ];
+        }
+        (0, _pseudoElements.movePseudos)(sel);
+    });
+    return `${important} ${sel.toString()}`;
+}