bug: Weekly Target progress resets to totalSolved on transient API failure (#297)

[yashvi-3106]

Description

Fixes the issue where a user's weekly target baseline count (goal.baseCount) would get overwritten or initialized to 0 during a transient API failure (such as rate limits or network issues) on profile page load. This prevented progress from resetting correctly and immediately marked targets as completed.

Linked Issue

Fixes #297

Changes Made

• Refactored fetchSolvedCount() to propagate fetch failures and network errors instead of defaulting to returning 0.
• Caught errors in render() so that the baseline count is not initialized to 0 when the API fails on load. Instead, the UI displays [ FAILED TO SYNC PROGRESS ] in red.
• Wrapped the save button handler in a try-catch block to verify the API response before saving the target to localStorage. If it fails, the input border turns red and updates the placeholder to "API Error, retry".
• Added a focus event listener to reset the target input field's error states and restore the default placeholder.

Type of Change

• Bug fix
• New feature
• UI/Visual update
• Documentation update
• Refactor

Testing

• Tested locally
• Tested on mobile viewport (if applicable)
• No console errors introduced

Checklist

• My code follows the project's coding style
• I have formatted my code locally by running npx prettier --write . before submitting
• I am submitting my PR from a dedicated feature/* branch, not the main branch
• I have performed a self-review of my code
• My changes generate no new warnings or errors
• I have updated documentation if required
• I have linked the relevant issue

Screenshots / Screen Recording

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