feat: harden atoms-nexst against review findings (37 items)

Second review pass covering security, performance, admin tooling and the
public/room flows. All HIGH and MEDIUM findings from the audit are resolved;
nothing in this commit changes the visible feature set.

Authentication & session security
- CSP is now set on the request headers in the proxy, which is what Next.js
  uses to derive the render nonce, so the nonce is effective.
- 2FA: an already-enabled user cannot re-enroll, the setup endpoint is
  rate-limited per account, and confirmed codes are persisted so the second
  secret no longer silently never applies.
- Password reset revokes the ticket, authTicket and all personal access
  tokens, and bumps the token version so existing sessions die. The same
  revocation is now wired into the staff-side password reset.
- /reset and /verify return a stable error code instead of raw text; the
  mail lookups are ordered by id so duplicates cannot vary between runs.
- Resending the verification mail gets a per-address cooldown on top of the
  per-user limit.
- Issue API tokens with the narrower radio/ticket ability set instead of "*".

Authorization & input handling
- Mid-rank staff can no longer keep dynamically granted non-view admin.*
  permissions: existing grants are revoked by migration and the grant lookup
  is restricted to "%.view". Rank guards use the dynamic super-admin check.
- Alerting a user is permission-checked and audited like the other tools.
- Material mutations (giveCredits/giveDuckets/giveDiamonds, the admin user
  actions route, bulk user actions) are capped and rank-guarded, and bulk
  ids are bounded.
- updateRoom / updateRoomItem write through a field allowlist, and items
  may only be edited through their own room.
- Classnames reaching the filesystem are validated before use so a crafted
  value cannot escape the asset directories.
- The word filter now also covers offline mails, guild forum threads and
  replies, and user mottos.
- Media uploads are validated by magic bytes, /api/media requires the page
  edit permission, APP_URL must be configured once mail is enabled, and the
  diagnostics error route checks the fetch site header.

Admin tooling
- Secret settings render masked and cannot be overwritten with a blank or
  an arbitrary raw key; radio credentials are new password inputs.
- Commandocentrum balance changes are audited.
- Admin list pagination reads the caller's per-page instead of the max, and
  the log exporter caps offset and search length.

Performance
- Catalog translations are cached per module, with a cheap revision hash;
  the public online count uses a stale window instead of hammering the DB.
- The cache warmup now primes the payload the home route actually reads.
- TopHeader batches its queries into one round trip, and LCP avatars load
  eagerly.
- motion/react and sonner are no longer part of the root layout; the nav
  dropdown and mobile nav panels are lazy client chunks. Anonymous visitors
  again get the navigation chrome, and public pages get an edge cacheable
  response.

Accessibility
- Nested <main> elements in phase pages became <section>; the page entrance
  and route progress animations are pure CSS that respect reduced motion.

src/actions/admin-media.ts

@@ -4,11 +4,32 @@ import { mkdir, writeFile } from "node:fs/promises";
 import path from "node:path";
 import { revalidatePath } from "next/cache";
 import { requirePermission } from "@/lib/admin/guard";
+import { validateSiteImageUpload } from "@/lib/images/site-image-upload";
 import { MEDIA_ROOT, resolveMediaPath } from "@/lib/media-storage";
 import { PERMS } from "@/lib/permissions";
 
-const MAX_SIZE = 5 * 1024 * 1024; // 5MB
-const ALLOWED = ["image/png", "image/jpeg", "image/gif", "image/webp"];
+/**
+ * Store an uploaded media file under MEDIA_ROOT.
+ *
+ * The extension always comes from the *detected* format (magic bytes + a full
+ * sharp decode), never from `file.name` or the browser-supplied MIME type:
+ * trusting either lets arbitrary bytes land on disk with an attacker-chosen name
+ * that the media route would then serve.
+ */
+async function storeUploadedMedia(
+	file: File,
+): Promise<{ ok: true; name: string } | { ok: false; error: string }> {
+	const validated = await validateSiteImageUpload(file);
+	if (!validated.success) return { ok: false, error: validated.error };
+	const baseDir = MEDIA_ROOT;
+	await mkdir(baseDir, { recursive: true });
+	const name = `${Date.now()}-${Math.random().toString(36).slice(2, 8)}.${validated.extension}`;
+	const filePath = resolveMediaPath(name);
+	if (!filePath.startsWith(baseDir + path.sep))
+		return { ok: false, error: "Invalid path" };
+	await writeFile(filePath, validated.bytes);
+	return { ok: true, name };
+}
 
 export async function uploadMedia(
 	formData: FormData,
@@ -16,25 +37,9 @@ export async function uploadMedia(
 	await requirePermission(PERMS.PAGES_EDIT);
 	const file = formData.get("file") as File | null;
 	if (!file || file.size === 0) return { ok: false, error: "No file provided" };
-	if (file.size > MAX_SIZE)
-		return { ok: false, error: "File too large (max 5MB)" };
-	if (!ALLOWED.includes(file.type))
-		return {
-			ok: false,
-			error: "Invalid file type. Allowed: PNG, JPEG, GIF, WebP",
-		};
 
-	const baseDir = MEDIA_ROOT;
-	// eslint-disable-next-line security/detect-non-literal-fs-filename
-	await mkdir(baseDir, { recursive: true });
-
-	const ext = file.name.split(".").pop() ?? "png";
-	const name = `${Date.now()}-${Math.random().toString(36).slice(2, 8)}.${ext}`;
-	const bytes = await file.arrayBuffer();
-	const filePath = resolveMediaPath(name);
-	if (!filePath.startsWith(baseDir + path.sep)) throw new Error("Invalid path");
-	// eslint-disable-next-line security/detect-non-literal-fs-filename
-	await writeFile(filePath, Buffer.from(bytes));
+	const stored = await storeUploadedMedia(file);
+	if (!stored.ok) return { ok: false, error: stored.error };
 
 	revalidatePath("/api/media");
 	revalidatePath("/admin/media");
@@ -45,6 +50,8 @@ export async function deleteMedia(name: string): Promise<void> {
 	await requirePermission(PERMS.PAGES_EDIT);
 	const { unlink } = await import("node:fs/promises");
 	const baseDir = MEDIA_ROOT;
+	// A name that is not a bare file name never reaches the unlink.
+	if (name.includes("/") || name.includes("\\") || name.includes("..")) return;
 	const filePath = resolveMediaPath(name);
 	if (!filePath.startsWith(baseDir + path.sep)) return;
 	try {
@@ -62,22 +69,11 @@ export async function uploadMediaAndReturn(
 	await requirePermission(PERMS.PAGES_EDIT);
 	const file = formData.get("file") as File | null;
 	if (!file || file.size === 0) return "";
-	if (file.size > MAX_SIZE) return "";
-	if (!ALLOWED.includes(file.type)) return "";
 
-	const baseDir = MEDIA_ROOT;
-	// eslint-disable-next-line security/detect-non-literal-fs-filename
-	await mkdir(baseDir, { recursive: true });
-
-	const ext = file.name.split(".").pop() ?? "png";
-	const name = `${Date.now()}-${Math.random().toString(36).slice(2, 8)}.${ext}`;
-	const bytes = await file.arrayBuffer();
-	const filePath = resolveMediaPath(name);
-	if (!filePath.startsWith(baseDir + path.sep)) return "";
-	// eslint-disable-next-line security/detect-non-literal-fs-filename
-	await writeFile(filePath, Buffer.from(bytes));
+	const stored = await storeUploadedMedia(file);
+	if (!stored.ok) return "";
 
 	revalidatePath("/api/media");
 	revalidatePath("/admin/media");
-	return `/api/media/${name}`;
+	return `/api/media/${stored.name}`;
 }