docs(docs): restructure guides into numbered groups and add meta files

apps/docs/content/guides/(1-data-structures)/meta.ts

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+import { defineMeta } from "blume";
+
+export default defineMeta({ title: "Data Structures", order: 1 });

apps/docs/content/guides/(2-algorithms)/meta.ts

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+import { defineMeta } from "blume";
+
+export default defineMeta({ title: "Algorithms", order: 2 });

apps/docs/content/guides/(3-techniques)/meta.ts

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+import { defineMeta } from "blume";
+
+export default defineMeta({ title: "Techniques", order: 3 });