fix(security): audit completo — secondo gate admin, hardening slug, XSS, CSP/HSTS, update CVE

Audit di sicurezza su tutta l'app. Report in .planning/SECURITY-SCAN.md (codice),
.planning/SECURITY-AUDIT-INFRA.md (dipendenze/segreti/deploy) e piano in
.planning/SECURITY-REMEDIATION-PLAN.md.

CRITICO — l'autorizzazione admin era un unico punto di rottura: nessuna delle 21
pagine /admin controllava la sessione e admin/layout.tsx renderizzava comunque i
figli quando mancava. L'unico guard era proxy.ts, su un Next.js affetto da
GHSA-6gpp-xcg3-4w24 (proxy bypass). Ora il layout è un secondo gate indipendente;
proxy.ts marca il path con un token derivato da NEXTAUTH_SECRET, così il gate non
è aggirabile forgiando header e fallisce chiuso se il proxy non gira.

ALTO — gli slug cliente avevano 4 caratteri casuali da Math.random() (~20 bit,
1.7M tentativi) e risolvono prima del token: ora 12 caratteri via nanoid
(CSPRNG, ~62 bit). Aggiunto rate limit al ramo /client/, che ne era privo.

ALTO — src/lib/quote-actions.ts esponeva due server action pubbliche senza
autenticazione, una delle quali scriveva su DB. Codice morto, zero chiamanti:
rimosso.

MEDIO — i quattro dangerouslySetInnerHTML nelle sezioni proposta rendevano output
AI come HTML grezzo su pagina pubblica, alimentato da transcript di terzi. Sostituiti
con RichText (whitelist di emphasis, nessun HTML al DOM). I transcript ora sono
recintati in tag che il system prompt dichiara essere dati, non istruzioni.

Inoltre: next 16.2.6 -> 16.2.12 e next-auth 4.24.14 -> 4.24.15 (chiude 9 CVE Next
piu GHSA-xmf8-cvqr-rfgj su getToken, raggiungibile dal proxy); HSTS e CSP;
potatura della Map di rate-limit.ts, che cresceva senza limite; espunta la password
Postgres di produzione dai due 07-01-SUMMARY.md.

Verificato: tsc pulito, build OK, smoke test su login/redirect/header forgiati.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

src/components/public/proposal/RichText.tsx

@@ -0,0 +1,43 @@
+import { Fragment } from "react";
+
+/**
+ * Renders AI-generated proposal strings with emphasis, without ever handing raw
+ * HTML to the DOM.
+ *
+ * These strings come from Claude (src/lib/proposal/agent.ts), which builds its
+ * prompt from client transcripts — third-party text. They were previously
+ * rendered with dangerouslySetInnerHTML on the public /preventivo/[slug] page,
+ * so a successful prompt injection became stored XSS against the prospect
+ * (C-4 in .planning/SECURITY-SCAN.md). The prompt never asks for HTML in the
+ * first place; the only markup worth keeping is emphasis.
+ *
+ * Recognises **bold** and <strong>/<b> and turns them into real React elements.
+ * Anything else — including <img onerror>, <script>, stray angle brackets — is
+ * emitted as text by React's normal escaping.
+ */
+
+// No dotAll flag: emphasis is not expected to span lines, and the project's
+// TS target predates es2018.
+const PATTERN = /\*\*(.+?)\*\*|<(?:strong|b)>(.+?)<\/(?:strong|b)>/gi;
+
+export function RichText({ children }: { children: string }) {
+  const parts: React.ReactNode[] = [];
+  let cursor = 0;
+
+  for (const match of children.matchAll(PATTERN)) {
+    const at = match.index;
+    if (at > cursor) parts.push(children.slice(cursor, at));
+    parts.push(<strong key={at}>{match[1] ?? match[2]}</strong>);
+    cursor = at + match[0].length;
+  }
+
+  if (cursor < children.length) parts.push(children.slice(cursor));
+
+  return (
+    <span>
+      {parts.map((p, i) => (
+        <Fragment key={i}>{p}</Fragment>
+      ))}
+    </span>
+  );
+}

src/components/public/proposal/sections/DeliverablesSection.tsx

@@ -1,5 +1,6 @@
 import type { ProposalContent } from "@/lib/proposal/schema";
 import { X } from "lucide-react";
+import { RichText } from "@/components/public/proposal/RichText";
 
 type Props = { deliverables: ProposalContent["deliverables"] };
 
@@ -18,7 +19,7 @@ export function DeliverablesSection({ deliverables }: Props) {
             {deliverables.deliverables.map((d, i) => (
               <li key={i} className="flex items-start gap-2 text-sm text-foreground">
                 <span className="text-primary mt-0.5">›</span>
-                <span dangerouslySetInnerHTML={{ __html: d }} />
+                <RichText>{d}</RichText>
               </li>
             ))}
           </ul>

src/components/public/proposal/sections/ScopeSection.tsx

@@ -1,5 +1,6 @@
 import type { ProposalContent } from "@/lib/proposal/schema";
 import { CheckCircle2 } from "lucide-react";
+import { RichText } from "@/components/public/proposal/RichText";
 
 type Props = { scope: ProposalContent["scope"] };
 
@@ -28,7 +29,7 @@ export function ScopeSection({ scope }: Props) {
             {scope.objectives.map((obj, i) => (
               <li key={i} className="flex items-start gap-2 text-sm text-foreground">
                 <CheckCircle2 size={14} className="text-primary mt-0.5 shrink-0" />
-                <span dangerouslySetInnerHTML={{ __html: obj }} />
+                <RichText>{obj}</RichText>
               </li>
             ))}
           </ul>

src/components/public/proposal/sections/SolutionNodeSection.tsx

@@ -1,4 +1,5 @@
 import type { SolutionNode } from "@/lib/proposal/schema";
+import { RichText } from "@/components/public/proposal/RichText";
 
 type Props = { solution: SolutionNode };
 
@@ -25,7 +26,7 @@ export function SolutionNodeSection({ solution }: Props) {
           {solution.throughWhat.map((item, i) => (
             <li key={i} className="flex items-start gap-2 text-sm text-foreground">
               <span className="text-primary mt-0.5">›</span>
-              <span dangerouslySetInnerHTML={{ __html: item }} />
+              <RichText>{item}</RichText>
             </li>
           ))}
         </ul>

src/components/public/proposal/sections/StrategistSection.tsx

@@ -1,5 +1,6 @@
 import type { ConsultantProfile } from "@/lib/proposal/profile";
 import { CheckCircle2 } from "lucide-react";
+import { RichText } from "@/components/public/proposal/RichText";
 
 type Props = { consultant: ConsultantProfile };
 
@@ -33,7 +34,7 @@ export function StrategistSection({ consultant }: Props) {
             {consultant.credentials.map((c, i) => (
               <li key={i} className="flex items-start gap-2 text-sm text-muted-foreground">
                 <CheckCircle2 size={14} className="text-primary mt-0.5 shrink-0" />
-                <span dangerouslySetInnerHTML={{ __html: c }} />
+                <RichText>{c}</RichText>
               </li>
             ))}
           </ul>