refactor(core): Implement dynamic navigation

[serafim-san]

Description

This PR introduces a major architectural refactor to improve project scalability, developer experience (DX), and type safety.

Key Changes

1. Dynamic Sidebar & Navigation

• Removed hardcoded navigation logic. The sidebar is now auto-generated based on the folder hierarchy in src/content/docs.
• Source: Nested folders (e.g., docs/getting-started/intro.md) provide logical grouping for the sidebar.
• Output: Flat URLs (e.g., /intro) are preserved to maintain SEO and backward compatibility.

2. Routing Safety Mechanism

• Implemented Build-Time Validation to prevent slug collisions.
• Since the routing flattens the directory structure, the build will now fail explicitly if two files from different folders claim the same URL, ensuring production safety.

**3. Modular Architecture Restructured the codebase to ensure better separation of concerns and modularity:

src/modules/ - encapsulated domain logic (Navigation engine, Docs processing).

src/components/features/ - feature-specific components (e.g., Search).

src/components/layout/, ui/ & shared/ - reusable UI and structural components.

src/config/ - centralized project configuration (Navigation, SEO, Products).

4. TypeScript Coverage

5. Content Configuration (Frontmatter)

Introduced new schema to control sidebar

sidebar: z.object({
  label: z.string().optional(),
  order: z.number().default(999),
  hidden: z.boolean().default(false),
}).default({}),

Example of usage:

---
title: "Introduction to Santiment"
description: "Brief overview"
sidebar:
  label: "Intro"
  order: 1
---

Consistency check

❌ /404/ -- astro has a different page
❌ /email_login/ -- no longer supported
❌ /login/email/ -- no longer supported
❌ /login/email_login/ -- no longer supported
❌ /login/ -- no longer supported
➕ /education-and-use-cases/understanding-daily-active-addresses/ -- fixed mistype, added redirect for version with typo (understaning instead of understanDing)