feat(workouts): edit a hand-entered workout from its detail page

A workout logged by hand could only be deleted and logged again. The
detail page now offers an edit control beside delete for a MANUAL workout
carrying the form's `manual:` id, in one's own record. It opens the log
sheet on the stored values and saves by re-posting that id through
`POST /api/workouts/batch`, which already applies such a re-post as an
overwrite of that one row. No new route.

The overwrite nulls every overwritable column a re-post leaves out, and
the form has no fields for heart rate, steps, elevation or pauses. The
edit therefore sends those back as stored. A field left as shown sends the
stored value rather than one re-parsed from its display, so saving an
untouched edit keeps the start's seconds and a distance shown in miles at
its exact metres, and answers `duplicate`.

The detail read's `avgHr` / `maxHr` can come from a same-session twin;
the read now also serves the row's own `storedAvgHr` / `storedMaxHr`,
which is what the edit sends back.

docs/api/openapi.yaml

@@ -45064,6 +45064,22 @@ components:
               minimum: -9007199254740991
               maximum: 9007199254740991
             - type: "null"
+        storedAvgHr:
+          description: The row's own average heart rate (v1.42). `avgHr` may be filled in from a same-session twin by the
+            canonical picker; this is the stored value, which an edit of a hand-entered workout sends back so the twin's
+            value is not written onto it.
+          anyOf:
+            - type: integer
+              minimum: -9007199254740991
+              maximum: 9007199254740991
+            - type: "null"
+        storedMaxHr:
+          description: The row's own maximum heart rate (v1.42), as `storedAvgHr` is to `avgHr`.
+          anyOf:
+            - type: integer
+              minimum: -9007199254740991
+              maximum: 9007199254740991
+            - type: "null"
         stepCount:
           anyOf:
             - type: integer