refactor: feedback form contains dead/abandoned code

## Current State:

`FeedbackForm.tsx` contains dead code from an abandoned feature:
An unused `useMutation` block (lines 81-100) that posts to a non-existent `localhost:3001/text_extraction` endpoint. The mutation is never triggered — only its `isLoading` value is used by the submit button.
~50 lines of commented-out image attachment submission logic (lines 127-178)
~70 lines of commented-out image attachment UI (lines 354-421)
The actual form submission is handled by onSubmit (line 112), which works fine independently.

It looks like the image submission feature was abandoned. The commented out code looks irrelevant now, since it included a Jira integration. Just remove it and we can come back to this later if we want to allow image attachments in the feedback form.

## Changes needed:
Remove the `useMutation` block, all commented-out code, and any unused imports (e.g. `useMutation` from react-query). The submit button (around line 433) references `isLoading` from the removed mutation.

Inizia in FeedbackForm.tsx esaminando il blocco useMutation, le sezioni commentate di submission e UI e il riferimento isLoading del pulsante di invio. Rimuovi il codice abbandonato e gli import inutilizzati, quindi assicurati che il pulsante non dipenda più dalla mutation rimossa, preservando il flusso onSubmit esistente. Esegui i controlli frontend del progetto per confermare che il form funzioni ancora.

Scritto dal modello di indicizzazione a partire dal testo della issue.