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/css-tree/cjs/syntax/node/Rule.cjs

@@ -0,0 +1,58 @@
+'use strict';
+
+const types = require('../../tokenizer/types.cjs');
+
+function consumeRaw(startToken) {
+    return this.Raw(startToken, this.consumeUntilLeftCurlyBracket, true);
+}
+
+function consumePrelude() {
+    const prelude = this.SelectorList();
+
+    if (prelude.type !== 'Raw' &&
+        this.eof === false &&
+        this.tokenType !== types.LeftCurlyBracket) {
+        this.error();
+    }
+
+    return prelude;
+}
+
+const name = 'Rule';
+const walkContext = 'rule';
+const structure = {
+    prelude: ['SelectorList', 'Raw'],
+    block: ['Block']
+};
+
+function parse() {
+    const startToken = this.tokenIndex;
+    const startOffset = this.tokenStart;
+    let prelude;
+    let block;
+
+    if (this.parseRulePrelude) {
+        prelude = this.parseWithFallback(consumePrelude, consumeRaw);
+    } else {
+        prelude = consumeRaw.call(this, startToken);
+    }
+
+    block = this.Block(true);
+
+    return {
+        type: 'Rule',
+        loc: this.getLocation(startOffset, this.tokenStart),
+        prelude,
+        block
+    };
+}
+function generate(node) {
+    this.node(node.prelude);
+    this.node(node.block);
+}
+
+exports.generate = generate;
+exports.name = name;
+exports.parse = parse;
+exports.structure = structure;
+exports.walkContext = walkContext;