fix(ui): seed QRs use the SeedQR standard so hardware wallets can scan them

Plain-text seed QRs didn't scan into Passport Prime — wallets that
import seeds by QR (Passport, SeedSigner, Keystone, Nunchuk, Sparrow)
expect the SeedQR standard: each BIP39 word as its zero-padded 4-digit
wordlist index, concatenated into a numeric QR.

- new utils/seedqr.ts encodes BIP39 words per the SeedSigner spec
  (@scure/bip39 wordlist; vector-checked abandon=0000, zoo=2047)
- new shared SeedRevealPanel (Words/QR tabs, tap-to-reveal blur) now
  backs the LND reveal AND the Settings→Backup recovery-phrase reveal,
  so every current and future seed reveal behaves the same
- onboarding seed + Settings reveal: QR defaults to SeedQR with a
  plain-text toggle
- LND seed stays plain-text-only with an explicit note: aezeed is not
  BIP39 and only restores into LND-based wallets (Zeus/Blixt/another
  node) — SeedQR-encoding it would just mislead

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

neode-ui/src/utils/seedqr.ts

@@ -0,0 +1,21 @@
+/**
+ * SeedQR encoding (SeedSigner standard, supported by Passport/Passport Prime,
+ * SeedSigner, Keystone, Nunchuk, Sparrow, …): each BIP39 word becomes its
+ * zero-padded 4-digit wordlist index (0000–2047), concatenated into one
+ * digit stream and rendered as a numeric-mode QR. A 24-word seed is 96
+ * digits. Spec: github.com/SeedSigner/seedsigner/blob/main/docs/seed_qr
+ *
+ * Only valid for real BIP39 mnemonics — LND's aezeed shares the wordlist but
+ * is NOT BIP39, and hardware wallets cannot import it; never SeedQR-encode it.
+ */
+export async function toSeedQrDigits(words: string[]): Promise<string | null> {
+  if (words.length === 0) return null
+  const { wordlist } = await import('@scure/bip39/wordlists/english.js')
+  const digits: string[] = []
+  for (const raw of words) {
+    const idx = wordlist.indexOf(raw.trim().toLowerCase())
+    if (idx < 0) return null // not a BIP39 word — caller falls back to text
+    digits.push(idx.toString().padStart(4, '0'))
+  }
+  return digits.join('')
+}