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/lib/rate-limit.ts

@@ -47,12 +47,21 @@ export async function rateLimit(
 	if (redis) {
 		try {
 			const windowKey = `ratelimit:${key}`;
-			const current = await redis.incr(windowKey);
-			if (current === 1) await redis.pexpire(windowKey, windowMs);
-			const ttl =
-				current === 1 ? windowMs : Math.max(0, await redis.pttl(windowKey));
+			// One atomic round trip: INCR + PEXPIRE in a single Lua call. Two
+			// separate commands left keys without a TTL whenever the process died
+			// in between, which permanently locked that client out.
+			const [current, ttl] = (await redis.eval(
+				`local c = redis.call('INCR', KEYS[1])
+				 if c == 1 then redis.call('PEXPIRE', KEYS[1], ARGV[1]) end
+				 local t = redis.call('PTTL', KEYS[1])
+				 if t < 0 then t = tonumber(ARGV[1]) end
+				 return {c, t}`,
+				1,
+				windowKey,
+				String(windowMs),
+			)) as [number, number];
 			if (current > limit) {
-				return { ok: false, retryAfter: Math.ceil(ttl / 1000) };
+				return { ok: false, retryAfter: Math.max(1, Math.ceil(ttl / 1000)) };
 			}
 			return { ok: true, retryAfter: 0 };
 		} catch {
@@ -64,6 +73,9 @@ export async function rateLimit(
 				);
 			}
 		}
+	} else if (redisFailWarned) {
+		redisFailWarned = false;
+		logger.info("[rate-limit] Redis available again — shared limits restored.");
 	}
 
 	cleanup();