docs: resolve recipe-quota semantics decision in HANDOFF.md

Keep maxRecipes as a creations-per-month counter; deleting a recipe does
not free up quota. No code change needed, current behavior already matches.

HANDOFF.md

@@ -94,7 +94,7 @@ A full 4-agent audit (bugs / UI-UX / backend consistency / feature gaps) was run
     - `app/api/v1/search/route.ts:72` — escape `%`/`_` in ilike; `feed/trending/route.ts:6` — parseInt NaN reaches `.limit()`.
     - `app/api/v1/shopping-lists/[id]/items/[itemId]/route.ts:17` — body cast without Zod.
     - `app/api/v1/meal-plans/[weekStart]/entries/route.ts:48` — `recipeId` unvalidated → FK violation 500 (sibling shared route validates; copy it).
-    - Recipe usage counter monthly + never decremented on delete → `maxRecipes` = "creations per month". Decide semantics.
+    - ~~Recipe usage counter monthly + never decremented on delete~~ — **decided**: keep as-is, `maxRecipes` means "creations per month," deleting a recipe does not free up quota.
     - `lib/ai/resolve-user-key.ts:18-23,44-62` — BYOK decrypt failures silently fall back to platform key; surface error.
     - API keys: no expiry/scopes; all of a user's keys share one rate bucket (`api-auth.ts:79`).