feat: add product concept subtitle to radars

A Radar gains an optional Concept — a short subtitle naming the product
and its typical performances, rendered under the title and wrapping to a
balanced second line when long. Old radars default to an empty Concept
on load.

src/storage.ts

@@ -9,7 +9,9 @@ function loadAll(): Radar[] {
     const raw = localStorage.getItem(STORAGE_KEY)
     if (!raw) return []
     const parsed = JSON.parse(raw)
-    return Array.isArray(parsed) ? parsed : []
+    if (!Array.isArray(parsed)) return []
+    // Default concept for radars saved before the field existed.
+    return parsed.map((r: Radar) => ({ ...r, concept: r.concept ?? '' }))
   } catch {
     return []
   }
@@ -80,6 +82,7 @@ export function useRadars() {
     const radar: Radar = {
       id: uid(),
       name,
+      concept: '',
       criteria,
       profiles,
       scores: {},