feat: client edit/delete/archive + time tracker + analytics time section

Schema:
- clients.archived boolean (default false)
- time_entries table (client_id, started_at, ended_at, duration_seconds)

Client management:
- /admin/clients/[id]/edit — form pre-compilato con nome, brand, brief
- ClientActions: Modifica / Archivia / Elimina con doppia conferma
- setClientArchived: toggle archiviazione senza perdere dati
- deleteClient: elimina con cascade, redirect a /admin
- Admin list: toggle "Mostra archiviati" via ?archived=1, righe archiviate opache

Time tracker:
- startTimer: crea sessione, ferma automaticamente quella precedente
- stopTimer: chiude sessione, calcola duration_seconds
- TimerCell: ▶/⏹ per ogni cliente, contatore live in secondi, totale cumulativo
- Una sola sessione attiva alla volta su tutta la lista

Analytics:
- Sezione "Fatturato" (invariata) + sezione "Tempo tracciato" separata
- Ore totali per anno + barre orizzontali per cliente
- getTotalTrackedHours, getTimeByClient queries

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/app/admin/clients/[id]/actions.ts

@@ -1,6 +1,7 @@
 "use server";
 
 import { revalidatePath } from "next/cache";
+import { redirect } from "next/navigation";
 import { db } from "@/db";
 import {
   phases,
@@ -14,6 +15,38 @@ import {
 import { eq } from "drizzle-orm";
 import { z } from "zod";
 
+// ── CLIENT CRUD ───────────────────────────────────────────────────────────────
+
+const clientSchema = z.object({
+  name:       z.string().min(1, "Nome richiesto"),
+  brand_name: z.string().min(1, "Brand name richiesto"),
+  brief:      z.string(),
+});
+
+export async function updateClient(clientId: string, formData: FormData) {
+  const parsed = clientSchema.safeParse({
+    name:       formData.get("name"),
+    brand_name: formData.get("brand_name"),
+    brief:      formData.get("brief") ?? "",
+  });
+  if (!parsed.success) throw new Error(parsed.error.issues[0].message);
+  await db.update(clients).set(parsed.data).where(eq(clients.id, clientId));
+  revalidatePath(`/admin/clients/${clientId}`);
+  revalidatePath("/admin");
+}
+
+export async function deleteClient(clientId: string) {
+  await db.delete(clients).where(eq(clients.id, clientId));
+  revalidatePath("/admin");
+  redirect("/admin");
+}
+
+export async function setClientArchived(clientId: string, archived: boolean) {
+  await db.update(clients).set({ archived }).where(eq(clients.id, clientId));
+  revalidatePath(`/admin/clients/${clientId}`);
+  revalidatePath("/admin");
+}
+
 // ── PHASES ────────────────────────────────────────────────────────────────────
 
 export async function addPhase(clientId: string, formData: FormData) {