feat: mypy for all type check

[yihong0618]

Summary

This maybe a huge Pull Request, the main goal is to make all the mypy type check passed to fix the potential bugs So its still WIP and will be draft. and try to close https://github.com/langgenius/dify/issues/10928

the first steps had beed done. -> let mypy work in api folder. And we fixed some of them,

you can check by

• gh pr checkout 10921

• when found small bug fix in main branch first

• install mypy

• cd api && mypy .

• [x] make it work for mypy

• [ ] add ci for it

• [ ] always merge main for the latest code

• [ ] fixed them folder by folder, maybe type by type

for now after this commit it still has 4261 errors

some details update here:

• https://github.com/pallets-eco/flask-sqlalchemy/issues/1327

@laipz8200 @crazywoola

[!Tip] Close issue syntax: Fixes #<issue number> or Resolves #<issue number>, see documentation for more details.

Screenshots

Before:	After:
...	...

Checklist

[!IMPORTANT]
Please review the checklist below before submitting your pull request.

• [ ] This change requires a documentation update, included: Dify Document
• [x] I understand that this PR may be closed in case there was no previous discussion or issues. (This doesn't apply to typos!)
• [x] I've added a test for each change that was introduced, and I tried as much as possible to make a single atomic change.
• [x] I've updated the documentation accordingly.
• [x] I ran dev/reformat(backend) and cd web && npx lint-staged(frontend) to appease the lint gods