[schema] Emit unit for float fields; leave union validators untyped

Address review feedback:
- float_with_unit fields now dump as type "float" with the canonical unit
  (e.g. {"type": "float", "unit": "Hz"}) rather than the quantity name as the
  type. This keeps the type vocabulary closed and lets editors label the field
  with its unit directly instead of mapping each quantity name. The unit is the
  first alternative of the accepted-units regex; current/voltage list A/V first
  (no validation change).
- Drop scalar typing of validate_bytes and date_time: both accept multiple YAML
  forms (unit-suffixed strings or numbers, and a formatted string or a mapping)
  that a single scalar type would wrongly reject in the editor.

script/build_language_schema.py

@@ -155,12 +155,7 @@ _CV_STRING_VALIDATORS = (
     cv.dimensions,
     cv.none,
 )
-_CV_INTEGER_VALIDATORS = (
-    cv.hex_int,
-    cv.percentage_int,
-    cv.mqtt_qos,
-    cv.validate_bytes,
-)
+_CV_INTEGER_VALIDATORS = (cv.hex_int, cv.percentage_int, cv.mqtt_qos)
 _CV_FLOAT_VALIDATORS = (
     cv.percentage,
     cv.possibly_negative_percentage,
@@ -1129,10 +1124,12 @@ def convert(schema, config_var, path):
             config_var["registry"] = "light.effects"
             config_var["filter"] = data[0]
         elif schema_type == "float":
-            # cv.float_with_unit returns its quantity name (e.g. "frequency")
-            # for SCHEMA_EXTRACT, so the field type is the specific quantity
-            # rather than a bare "float". Other float sources return None.
-            config_var[S_TYPE] = data if isinstance(data, str) else "float"
+            config_var[S_TYPE] = "float"
+            # cv.float_with_unit reports its canonical unit (e.g. "Hz", "V") for
+            # SCHEMA_EXTRACT; surface it next to the type so editors can label
+            # the field. Other float sources return None (no unit).
+            if isinstance(data, str):
+                config_var["unit"] = data
         elif schema_type in ("string", "integer", "time", "lambda"):
             # Scalar validators (e.g. cv.date_time) that declare their result
             # type via schema_extractor. ``data`` is unused (the decorated