fix(api,ui): Fix Kobo to Hardcover reading progress syncing

[suryavamsi6]

🚀 Pull Request

📝 Description

1. Fixes [Bug] Kobo-Hardcover Sync doesn't work as expected #2337 - Kobo-Hardcover sync only worked when KOReader-Hardcover sync was enabled

🛠️ Changes Implemented

1. Created a new user settings key called hardcoverKoboSyncEnabled
2. Add a radio button in the UI under the Kobo Integration Configuration section to enable Kobo-Hardcover Sync which in turn sets the key - hardcoverKoboSyncEnabled to true
3. This key is then used along side the existing hardcoverSyncEnabled key to check if Hardcover Sync is Enabled and then perform Hardcover Sync.
4. Modifications have been done in the classes where the existing flow was used.

🧪 Testing Strategy

1. All UI and Backend Tests ran successfully.
2. No Changes required in Backend Unit Tests
3. UI tests required minor change due to the inclusion of hardcoverApiKey

📸 Visual Changes (if applicable)

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⚠️ Required Pre-Submission Checklist

Please Read - This Checklist is Mandatory

Important Notice: We've experienced several production bugs recently due to incomplete pre-submission checks. To maintain code quality and prevent issues from reaching production, we're enforcing stricter adherence to this checklist.

All checkboxes below must be completed before requesting review. PRs that haven't completed these requirements will be sent back for completion.

Mandatory Requirements (please check ALL boxes):

• Code adheres to project style guidelines and conventions
• Branch synchronized with latest develop branch (please resolve any merge conflicts)
• 🚨 CRITICAL: Automated unit tests added/updated to cover changes (MANDATORY for ALL Spring Boot backend and Angular frontend changes - this is non-negotiable)
• 🚨 CRITICAL: All tests pass locally (run ./gradlew test for Spring Boot backend, and ng test for Angular frontend - NO EXCEPTIONS)
• 🚨 CRITICAL: Manual testing completed in local development environment (verify your changes work AND no existing functionality is broken - test related features thoroughly)
• Flyway migration versioning follows correct sequence (if database schema was modified)
• Documentation PR submitted to booklore-docs (required for features or enhancements that introduce user-facing or visual changes) - Add Hardcover Sync section in Kobo booklore-docs#29

Why This Matters:

Recent production incidents have been traced back to:

• Incomplete testing coverage (especially backend)
• Merge conflicts not resolved before merge
• Missing documentation for new features

Backend changes without tests will not be accepted. By completing this checklist thoroughly, you're helping maintain the quality and stability of Booklore for all users.

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