feat(settings): redesign the Import Key dialog

Rework the full-node Import Key dialog into a safer, Material-consistent, more
capable flow:

- Security: the key is masked by default (Password) with a reveal (eye) toggle,
  a DialogWarningHeader "only import a key you own" note, and the buffer is
  wiped with sodium_memzero on close and on successful import.
- Progress: import triggers a blocking full-chain rescan; the dialog now shows
  "Importing & rescanning — this can take several minutes" with LoadingDots and
  disables Import while it runs (no double-submit). Offline shows a "connect a
  running node" note and disables Import up front.
- Viewing keys: the classifier gains isViewingKey / isRecognizedImportKey;
  importPrivateKey auto-detects a shielded viewing key (zxviews…) and routes to
  z_importviewingkey (watch-only) vs z_importkey / importprivkey. The live type
  indicator shows Transparent / Shielded spending / Shielded viewing (watch-only).
- Result: on success the imported address is captured from the RPC result and
  shown via AddressCopyField.
- Material restyle (OverlayDialogSpec/BlurFloat + TactileButton + Esc) and full
  i18n (12 new keys x 8 languages; CJK subset rebuilt).

Verified: rendered on dark + light skins; a seeded zxviews… key shows the masked
field + "Shielded viewing key (watch-only)" indicator.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

res/lang/de.json

@@ -416,18 +416,30 @@
     "history": "Verlauf",
     "immature_type": "Unreif",
     "import": "Importieren",
+    "import_key_address": "Adresse:",
     "import_key_btn": "Schlüssel importieren",
+    "import_key_done": "Importiert. Wallet wird neu gescannt.",
+    "import_key_field": "Schlüssel",
     "import_key_formats": "Unterstützte Schlüsselformate:",
     "import_key_full_rescan": "(0 = vollständiger Rescan)",
+    "import_key_import": "Importieren",
     "import_key_label": "Privater Schlüssel:",
+    "import_key_need_node": "Verbinden Sie einen laufenden Node, um einen Schlüssel zu importieren.",
     "import_key_no_valid": "Keine gültigen Schlüssel in der Eingabe gefunden",
     "import_key_progress": "Importiere %d/%d...",
     "import_key_rescan": "Blockchain nach Import neu scannen",
+    "import_key_rescanning": "Import & erneuter Scan — das kann einige Minuten dauern",
+    "import_key_reveal_tip": "Schlüssel ein-/ausblenden",
     "import_key_start_height": "Starthöhe:",
     "import_key_success": "Schlüssel erfolgreich importiert",
     "import_key_t_format": "T-Adresse WIF private Schlüssel",
     "import_key_title": "Privaten Schlüssel importieren",
     "import_key_tooltip": "Geben Sie einen oder mehrere private Schlüssel ein, einen pro Zeile.\nUnterstützt sowohl z-Adresse als auch t-Adresse Schlüssel.\nZeilen die mit # beginnen werden als Kommentare behandelt.",
+    "import_key_type_tkey": "Transparenter privater Schlüssel",
+    "import_key_type_unknown": "Unbekanntes Schlüsselformat",
+    "import_key_type_zspend": "Abgeschirmter Ausgabeschlüssel",
+    "import_key_type_zview": "Abgeschirmter Anzeigeschlüssel (nur Lesen)",
+    "import_key_warn": "Importieren Sie nur einen Schlüssel, der Ihnen gehört — er gewährt Zugriff auf dessen Guthaben.",
     "import_key_warning": "Warnung: Teilen Sie niemals Ihre privaten Schlüssel! Das Importieren von Schlüsseln aus nicht vertrauenswürdigen Quellen kann Ihr Wallet gefährden.",
     "import_key_z_format": "Z-Adresse Ausgabeschlüssel (secret-extended-key-...)",
     "import_private_key": "Privaten Schlüssel importieren...",