frontend: NumberTextField gives each input its own id

Every NumberTextField had id="frame_time", so the ids repeated on a page
and a label could point at another field's input. The id now comes from
useId().

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01HVeDQsU5a8AJUdJPgWevAK

frontend/src/components/NumberTextField.tsx

@@ -1,4 +1,4 @@
-import {ChangeEvent, memo, ReactNode, useEffect, useState} from 'react';
+import {ChangeEvent, memo, ReactNode, useEffect, useId, useState} from 'react';
 
 import {
     InputAdornment, SxProps,
@@ -38,6 +38,8 @@ function NumberTextField({start_val, default: defaultValue, label, callback, cou
     const [text, setText] = useState(".");
     const [err, setErr] = useState(true);
     const [val, setVal] = useState(0);
+    // Unique per field, so each label points at its own input
+    const id = useId();
 
     // Something has to change in parent to trigger setup => otherwise this makes infinite loop.
     // In case of error state start_val could stay same, but we want to return to "safe" set
@@ -79,7 +81,7 @@ function NumberTextField({start_val, default: defaultValue, label, callback, cou
         callback(new_val, new_err);
     };
 
-    return <TextField id="frame_time" label={label} variant="outlined"
+    return <TextField id={id} label={label} variant="outlined"
                       sx = {sx}
                       error={err}
                       onChange={updateValue}