Hashtags are being saved in lower case, leading to duplicate hashtags of the same name #5363

Pre-submission Checklist

• I have searched the existing issues and this bug has not been reported yet
• I have tested this issue on the demo site or the latest version

Where did you encounter this bug?

Latest stable version (self-hosted)

Memos Version

v0.25.3

Bug Description

Since the display of hashtags was changed to be lower case, my existing Memos are still showing as upper case, leading to new memos with the same hashtag being created as separate, lower case hastags.

For example:
"#House" - already exists in the list of hashtags

I create a new memo that contains "#House"
A new entry in the tag list is created called "#house"

Now, 2 tags exist, "#House" and "#house". Older Memos created before the update retain the upper case tag, newer ones create a new lower case tag.

Steps to Reproduce

Load a Memos instance with pre-existing tags
Create a new Memo using one of the pre-existing tags
Notice that 2 tags now exist, one in upper case, and a clone in lower case

Expected Behavior

Maybe Memos should update older posts with the new lowercase naming convention for tags to avoid duplicates?

Screenshots & Additional Context

No response