added architecture overview

[arpit2006]

Description

Closes: #603
Reference: #603

Added a comprehensive ARCHITECTURE.md file at the root of the project to outline the system architecture, folder structures, component dependencies, and design patterns utilized in the DevPath India Community Platform.

Key details included:

• System Architecture Flow: High-level Mermaid diagram mapping client browser, Next.js context/hooks, Firebase services, the Express assistant server, and third-party integrations (OpenRouter & GitHub).
• Client-Side Architecture: Detailed page routing tree, context managers description, and client state sequences.
• Backend Architecture: Explanation of the Express.js route orchestration and LLM multi-model failover/retry hierarchy.
• Database & Security: Outline of Firestore collections, schema relations, and access rules.
• Gamification & Points Sync Pipeline: Explanatory diagram showing GitHub sync and XP calculation criteria.

Type of change

• This change requires a documentation update

How Has This Been Tested?

• Local testing (verified Mermaid diagrams rendering syntax)

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings or errors
• I have checked that the "DevPath India" branding remains intact

[arpit2006]

@Aditya948351 , Requesting Review!

[arpit2006]

The build/test failures are unrelated to the additions in ARCHITECTURE.md. They are caused by Playwright strict-mode locator violations in the existing E2E tests:

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⚠️ Note on E2E Test Failures

The build/test failures are unrelated to the additions in ARCHITECTURE.md. They are caused by Playwright strict-mode locator violations in the existing E2E tests:

1. Login Test Failure (shows error alert when submitting invalid credentials):

   • Reason: page.locator('[role="alert"]') now matches two elements on the screen: the actual login error banner and the default Next.js __next-route-announcer__ div.
   • Suggested Fix: Target the error alert specifically, for example:

     const errorAlert = page.locator('div[role="alert"]').first(); 
     // or target by container class / excluding the route announcer:
     const errorAlert = page.locator('div[role="alert"]:not([id="__next-route-announcer__"])');

2. Roadmap Navigation Test Failures (learning paths page shows the h1 heading & "Back to Paths"):

   • Reason: page.getByRole('heading', { name: /learning paths/i }) matches both the <h1>Learning Paths</h1> title and the <h2>Structured Learning Paths</h2> subtitle.
   • Suggested Fix: Make the locator exact or specify the heading level:

     page.getByRole('heading', { name: 'Learning Paths', exact: true })
     // or
     page.getByRole('heading', { name: /learning paths/i, level: 1 })

[arpit2006]

@Aditya948351 , Can you add Appropriate Label!