Let plop notes be written from the UI (#85 item 5)

journal_entries.planting_id was modelled, accepted by the API, and the
JournalPanel already rendered a "planting" badge for such entries — but
nothing in the UI ever created one. A badge for a state the UI couldn't
produce.

Give the plop the same "add note" affordance the bed inspector has:
- PlopInspector gains an onAddNote button ("📓 Add a note about this
  plant"), shown only to an editor (a viewer can't write notes).
- The editor store gains a journalPlantingId scope beside journalObjectId.
  The two are mutually exclusive — each setter clears the other — so the
  journal filter is never double-scoped.
- JournalPanel filters by plantingId when that scope is set, shows a
  "Notes about one planting · Show all" banner, and its composer attaches
  new notes to the plop. Empty-state copy updated to match.

Two taps from a selected plant to typing, mirroring the bed flow. No
backend change — the API already accepted plantingId.

Co-Authored-By: Claude Opus 4.8 (1M context) <[email protected]>
Claude-Session: https://claude.ai/code/session_01H3zbym8Doka2d7D48maSgZ

web/src/editor/PlopInspector.tsx

@@ -25,6 +25,7 @@ export function PlopInspector({
   unit,
   onChangePlant,
   onClose,
+  onAddNote,
   readOnly = false,
 }: {
   plop: EditorPlanting
@@ -33,6 +34,9 @@ export function PlopInspector({
   unit: UnitPref
   onChangePlant: () => void
   onClose: () => void
+  /** Scope the journal to this plop and open it — the plop parallel of the bed
+   *  inspector's "add note" (#85). Absent for a viewer, who can't write notes. */
+  onAddNote?: () => void
   readOnly?: boolean
 }) {
   const update = useUpdatePlanting(gardenId)
@@ -172,6 +176,12 @@ export function PlopInspector({
         />
       </fieldset>
 
+      {!readOnly && onAddNote && (
+        <Button variant="ghost" className="justify-start px-2 py-1 text-sm" onClick={onAddNote}>
+          📓 Add a note about this plant
+        </Button>
+      )}
+
       {!readOnly && (
         <Button
           variant="ghost"