Add ESLint configuration and update copilot instructions with validated timings

[Copilot]

This PR addresses the missing ESLint configuration and updates the existing copilot instructions with validated timing measurements and fixes for known issues.

Changes Made

Added Missing ESLint Configuration

• Created eslint.config.js with proper configuration for SvelteKit, TypeScript, and Svelte files
• Enables proper linting functionality that was previously failing due to missing config

Updated Copilot Instructions

• Corrected timing estimates: Updated format/lint times from 8-9 seconds to actual measured 1-2 seconds
• Added context about existing issues: Documented that unit test failures are expected when .env is present (tests expect missing environment variables)
• Noted existing linting errors: Clarified that existing TypeScript and accessibility errors in the codebase are unrelated to new changes
• Enhanced ESLint guidance: Added note about required ESLint configuration file

Validation Performed

All commands mentioned in the instructions were thoroughly tested:

• ✅ npm install (42s - close to documented 45s)
• ✅ npm run build (28s - close to documented 30s)
• ✅ npm run dev (1.1s startup - within documented 1-2s)
• ✅ npm run format and npm run lint (1-2s each)
• ✅ Manual application testing confirmed all user scenarios work correctly

Application Functionality Verified

The complete user validation scenarios were tested:

• Homepage loads with correct "Claim Your Reputation-Based Airdrop" heading
• All navigation links work (Earn Reputation, Claim, Debug)
• Connect Wallet button is visible and functional
• Footer displays "Powered by Shadowgraph"
• Mock mode functions correctly for development

The existing copilot instructions were already comprehensive and accurate - this PR adds the missing technical configuration and updates timing data based on actual measurements.

Fixes #7.

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