feat: lead → client conversion + client contact fields (email/phone)

Blocco A+B (milestone v2.3). Migration 0011 is additive (ADD COLUMN only):
clients.email, clients.phone, leads.archived.

- createClientCore() extracted from createClient and reused by conversion
- clients.email/phone added to create + edit forms and shown on client header
  (never exposed on the public /client/[token] page)
- convertLeadToClient(): reuses core, carries over lead transcripts
  (client_transcripts.client_id), links project.created_from_lead_id,
  archives the lead while keeping its "won" status; idempotent
- "Converti in cliente" button on won leads; "Convertito → Apri cliente"
  once converted (clientId resolved via created_from_lead_id)
- archived leads hidden from list/kanban; detail page fetches by id incl. archived

Migration must be applied to the prod DB BEFORE this is deployed.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/db/schema.ts

@@ -21,6 +21,10 @@ export const clients = pgTable("clients", {
   name: text("name").notNull(),
   brand_name: text("brand_name").notNull(),
   brief: text("brief").notNull(),
+  // Contact fields (Phase v2.3) — carried over from a converted lead and used
+  // by the Email & Accesso (OTP) milestone. Admin-only, never exposed publicly.
+  email: text("email"),
+  phone: text("phone"),
   // token is SEPARATE from id — rotatable secret for client link access
   token: text("token")
     .notNull()
@@ -454,6 +458,9 @@ export const leads = pgTable("leads", {
   next_action: text("next_action"),
   next_action_date: timestamp("next_action_date", { withTimezone: true }),
   notes: text("notes"),
+  // Archive flag (v2.3) — a converted lead is hidden from the pipeline while
+  // keeping its "won" status, so the board doesn't fill up over time.
+  archived: boolean("archived").notNull().default(false),
   created_at: timestamp("created_at", { withTimezone: true })
     .notNull()
     .defaultNow(),