fix(signature): resolve signature component modified flag always firi…

[TanmayGaidhani]

fix(signature): resolve signature component modified flag always firing with false on user draw

Link to Jira Ticket

https://formio.atlassian.net/browse/FIO-XXXX

Description

What changed?

• Signature Component Patch: Added a runtime prototype monkey-patch to SignatureComponent.prototype.setValue inside Form.tsx. It temporarily intercepts this.triggerChange on the active component instance. If triggerChange is called without arguments (which standard @formio/js does right after a user strokes the signature pad, causing the debounced event queue to lose the flag), it forwards the original flags payload containing { modified: true }.
• Form Reconstruction Optimization: Wrapped formReadyCallback inside a React useRef to prevent the <Form /> component from destroying and recreating the underlying Webform instance whenever callback references update across renders.
• Automated Integration Test: Added Signature.test.tsx containing a test case to simulate signature stroke dispatching and assert that modified becomes true.

Why have you chosen this solution?

• Modifying the Signature component's prototype directly in the React wrapper allows React developers to get this critical bug fix immediately without needing to wait for a core @formio/js library release or affecting vanilla JS users.
• The lifecycle refactor prevents performance degradation and visual flickering in applications that pass inline handler functions (e.g., onFormReady={(form) => ...}).

Breaking Changes / Backwards Compatibility

• None. The change is non-breaking, fully backwards-compatible, and isolated to the signature component's change event propagation flow.

Dependencies

• None.

How has this PR been tested?

• Automated Test: Added an integration test suite under src/components/__tests__/Signature.test.tsx that simulates drawing on the signature pad canvas and verifies the change is received with the modified: true flag.
• Local Run: Executed tests locally via npm test src/components/__tests__/Signature.test.tsx.

Checklist:

• I have completed the above PR template
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation (if applicable)
• My changes generate no new warnings
• My changes include tests that prove my fix is effective (or that my feature works as intended)
• New and existing unit/integration tests pass locally with my changes
• Any dependent changes have corresponding PRs that are listed above