chore: remove signature save debug logging

[sandeep-2536]

What was there

SignatureTool.tsx had leftover development debug logging that ran every time a
user saved a signature. It logged the original file size, the outgoing payload
size, and request content-type/content-length details straight to the browser
console:

console.log('Original file size:', originalSize);
console.log('Payload size:', payloadSize);
console.log('Content-Type:', contentType);
console.log('Content-Length:', payloadSize);

This looked like instrumentation left over from development that was never
cleaned up before the feature shipped — it exposed internal request details
in the production console on every signature save.

Fix

• Removed all 4 console.log statements
• Removed the originalSize state variable, which existed only to feed these
  logs and had no other use in the component
• No functional/behavioral change — the signature save flow works exactly as
  before, just without the console noise

How this was found

Found via manual code review of the Tee signature flow, not from an assigned
GitHub issue.

Testing

• Added SignatureTool.test.tsx covering the upload-and-save flow to confirm
  behavior is unaffected by this cleanup
• Manually tested locally: drew/uploaded a signature, saved it, confirmed the
  request still succeeds and the debug logs no longer appear in console
• pnpm exec tsc --noEmit passes
• pnpm test — new SignatureTool.test.tsx passes. Note: 3 unrelated test
  suites (api.test.ts, PremiumTee.test.ts, GoldenTicketDetailPage.test.tsx)
  fail on main as well, due to a pre-existing tooling error
  (jsTokens is not a function) unrelated to this change.