feat: Add centralized ErrorService for consistent error handling

[TenFinges]

Description

Added a centralized ErrorService to handle errors consistently across the app. This replaces scattered error handling with a unified approach that provides user-friendly messages, accessibility support, and centralized logging.

Key changes:

• New ErrorService class with handle() and handleSilently() methods
• New ErrorType enum for categorizing errors (network, auth, storage, database, validation, general)
• Added 13 new localization strings for error messages
• Updated AuthenticationController, RoomsController, and CreateRoomController as pilot implementations

Fixes #722

Type of change

• New feature (non-breaking change which adds functionality)
• Refactor (does not change functionality, e.g. code style improvements, linting)

How Has This Been Tested?

• Added 14 unit tests for ErrorService covering:
  • User-friendly message generation for all error types
  • Appwrite-specific error handling (invalid credentials, user not found, etc.)
  • Silent error handling

flutter test test/services/error_service_test.dart
# 00:02 +14: All tests passed!

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
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• I have checked my code and corrected any misspellings

Maintainer Checklist

• closes Add centralized error handling service #722
• Tag the PR with the appropriate labels

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[github-actions]

🎉 Welcome @TenFinges!
Thank you for your pull request! Our team will review it soon. 🔍

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[TenFinges]

Please note that I've added the new error strings in English only. Previous contributors (or any native speakers) could contribute translations for Bengali, Hindi, Gujarati, Kannada, Marathi, and Punjabi.

[M4dhav]

Please fix merge conflicts