fix(garden): remove trailing slashes from openplantbook api urls and update label

Trailing slashes on /plant/search/ and /plant/detail/ caused Django to
return an HTML redirect page instead of JSON. SDK uses no trailing slashes.

Also updates the helper text to reference OpenPlantBook instead of Perenual.

src/modules/garden/components/plant-form.tsx

@@ -156,7 +156,7 @@ export function PlantForm({ existingPlant, defaultContainerId, containers }: Pro
           initialValue={existingPlant?.scientificName ?? ""}
         />
         <p className="text-xs text-[var(--ink-mute)]">
-          Search Perenual to auto-fill scientific name and care notes.
+          Search OpenPlantBook to auto-fill scientific name and care notes.
         </p>
       </div>