style: Integrate maven spotless plugin into project

[SYaoJun]

What changes were proposed in this pull request?

fix: #663

add spotless to pom.xml, run mvn spotless:apply automatically formatting the code.

How was this PR tested?

• Tests have Added for the changes
• Production environment verified

All tests have passed in local.

[SYaoJun]

This PR will change lots of files, do you have any suggestions? @Leomrlin

[SYaoJun]

I have reverted the full formatting of all Java files. As an initial step, it would be better to integrate Spotless into the project first, and then address the style issues incrementally.

[Leomrlin]

I have reverted the full formatting of all Java files. As an initial step, it would be better to integrate Spotless into the project first, and then address the style issues incrementally.

Good catch! This is a legit issue, but Spotless formatting would massively break historical code (think git blame nightmares 😅).
Let's not merge this yet – please send a DISCUSS thread to dev@geaflow.apache.org first so PMC + community can weigh in.

We’ll sort out a phased plan (new files only → gradual cleanup) together.