fix: Ccp-5454-validation-on-template-screens

[revanth-banala]

Description

Adds client-side max-length validation on the template create/edit
screens so users can't enter more text than the backend allows.

template title- max length 255
subject- max length 500
body- max length 10_000

Fixes # CCP-5454

Type of change

• Bug fix (non-breaking change which fixes an issue)

How Has This Been Tested?

• No new tests are required

Checklist

• I have read the CONTRIBUTING doc
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have already been accepted and merged

Further comments

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