fix(web): typecheck stricti per build di produzione

Quattro fix di tipi che emergono solo durante `next build` (con Next.js che esegue typecheck stretto su tutta l'app), pre-esistenti su main:

- `fast-timer.tsx`: l'omitted-vs-undefined di `exactOptionalPropertyTypes`
  rifiuta `{other: undefined}` per un campo opzionale. Costruisco l'oggetto
  symptoms condizionalmente.
- `plan-week.tsx`: `slots[0]` con `noUncheckedIndexedAccess` è `Slot |
  undefined`. Optional chaining `slots[0]?.meal`.
- `profile-form.tsx` e `weight-entry-form.tsx`: il mismatch Zod 3 + RHF
  + `exactOptionalPropertyTypes` sul tipo del Resolver è noto e non sistemabile
  senza upgrade. Cast locale del solo zodResolver, runtime invariato.

Lint pulito, 99/99 test verdi, `next build` ok in locale.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

apps/web/src/app/[locale]/fasting/fast-timer.tsx

@@ -257,13 +257,15 @@ function SymptomsDiary({ event }: { event: FastEventRow }) {
   function save(): void {
     startTransition(async () => {
       setSaved(false);
-      const result = await updateFastSymptoms(event.id, {
+      const symptoms: Parameters<typeof updateFastSymptoms>[1] = {
         headache,
         energy,
         hunger,
         clarity,
-        other: other.trim() || undefined,
+      };
-      });
+      const trimmedOther = other.trim();
+      if (trimmedOther) symptoms.other = trimmedOther;
+      const result = await updateFastSymptoms(event.id, symptoms);
       if (result.ok) {
         setSaved(true);
         window.setTimeout(() => setSaved(false), 2500);

apps/web/src/app/[locale]/plan/plan-week.tsx

@@ -139,7 +139,7 @@ export function PlanWeek({
           // Nessuno slot → giorno di digiuno completo (ESE_24).
           const isFastingDay = slots.length === 0;
           // Solo CENA con dailyKcal ridotto → giorno "leggero" del 5:2.
-          const isLightDay = !isFastingDay && slots.length === 1 && slots[0].meal === 'CENA';
+          const isLightDay = !isFastingDay && slots.length === 1 && slots[0]?.meal === 'CENA';
 
           return (
             <section key={dayKey} aria-labelledby={`day-${dayKey}`} className="space-y-5">

apps/web/src/app/[locale]/profile/profile-form.tsx

@@ -1,6 +1,11 @@
 'use client';
 
-import { zodResolver } from '@hookform/resolvers/zod';
+// eslint-disable-next-line @typescript-eslint/no-explicit-any
+import { zodResolver as zodResolverRaw } from '@hookform/resolvers/zod';
+// Cast: zod 3.x + RHF + exactOptionalPropertyTypes generano un mismatch noto;
+// il resolver runtime funziona, è solo un'incompatibilità sui tipi opzionali.
+// eslint-disable-next-line @typescript-eslint/no-explicit-any
+const zodResolver: any = zodResolverRaw;
 import {
   ACTIVITY_LEVELS,
   DIET_HISTORIES,

apps/web/src/app/[locale]/tracking/weight-entry-form.tsx

@@ -1,6 +1,11 @@
 'use client';
 
-import { zodResolver } from '@hookform/resolvers/zod';
+// eslint-disable-next-line @typescript-eslint/no-explicit-any
+import { zodResolver as zodResolverRaw } from '@hookform/resolvers/zod';
+// Cast: zod 3.x + RHF + exactOptionalPropertyTypes generano un mismatch noto;
+// il resolver runtime funziona, è solo un'incompatibilità sui tipi opzionali.
+// eslint-disable-next-line @typescript-eslint/no-explicit-any
+const zodResolver: any = zodResolverRaw;
 import { weightEntryInputSchema, type WeightEntryInput } from '@ketopath/shared';
 import { useTranslations } from 'next-intl';
 import { useState } from 'react';