fix(import): recognize real DragonX key formats in the import gate

The client-side pre-check rejected legitimate keys before the daemon ever
saw them, surfacing "Unrecognized key format" / a cryptic daemon "Invalid"
error. Two concrete defects plus the brittle heuristic behind them:

- Viewing keys: isViewingKey looked for Zcash's "zxview" extended-FVK
  prefix, but DragonX's z_exportviewingkey emits a Sapling *incoming*
  viewing key (HRP "zivks"), which z_importviewingkey is the only form the
  daemon decodes. Every real DragonX viewing key was refused. (F1)
- Uncompressed transparent WIF: the length+first-char heuristic accepted
  {5,K,L,U} only, but a version-188 uncompressed key starts with '7'. (F2)

Replace the heuristic with structural validation using the existing
checksum validators (F3): add util::decodeBase58Check (checksum-stripped
payload) and util::bech32Hrp (HRP of a valid Bech32 string). Transparent
keys are now accepted by decoding Base58Check and checking the payload is a
33/34-byte secret key with a DragonX SECRET_KEY version byte (188 main/
regtest, 128 testnet) — covering compressed and uncompressed, rejecting
addresses/typos by real checksum. Viewing keys are matched by the real
incoming-VK HRPs (zivks / zivktestsapling / zivkregtestsapling).

The Sweep gate and the dialog's live type indicator run off the same
predicates, so they are fixed too (F4). Messaging now names the likely
cause and appends a wrong-coin/network hint to the daemon's raw "Invalid"
error (F5).

Adds testPrivateKeyImportRecognition plus decodeBase58Check/bech32Hrp
coverage; suite green (1/1).

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

src/services/wallet_security_controller.cpp

@@ -1,9 +1,12 @@
 #include "wallet_security_controller.h"
 #include "../util/secure_vault.h"
+#include "../util/address_validation.h"
 
 #include <cctype>
+#include <cstdint>
 #include <cstdio>
 #include <utility>
+#include <vector>
 
 namespace dragonx {
 namespace services {
@@ -108,18 +111,35 @@ WalletSecurityController::KeyKind WalletSecurityController::classifyPrivateKey(c
 
 bool WalletSecurityController::isViewingKey(const std::string& key)
 {
-    // Sapling extended full viewing key (mainnet HRP "zxviews"; "zxview" also matches the prefix the
-    // lite backend recognizes). Watch-only: reveals the address's funds but cannot spend them.
-    return key.rfind("zxview", 0) == 0;
+    // DragonX's z_exportviewingkey returns a Sapling *incoming* viewing key (mainnet HRP "zivks");
+    // z_importviewingkey only decodes that form. Recognize it structurally — a valid Bech32 checksum
+    // plus a known HRP — instead of a bare prefix, and cover testnet/regtest too. (The old check
+    // looked for Zcash's "zxview" extended-FVK HRP, which DragonX never emits, so every real viewing
+    // key was rejected client-side.) Watch-only: reveals the address's funds but cannot spend them.
+    const std::string hrp = util::bech32Hrp(key);
+    return hrp == "zivks"                 // mainnet
+        || hrp == "zivktestsapling"       // testnet
+        || hrp == "zivkregtestsapling";   // regtest
 }
 
 bool WalletSecurityController::isRecognizedPrivateKey(const std::string& key)
 {
+    // Sapling z spending key (HRP "secret-extended-key-{main,test,regtest}"). These run ~300 chars,
+    // past the Bech32 length cap, so match by HRP prefix and let the daemon vet the payload.
     if (key.rfind("secret-extended-key-", 0) == 0) return true;               // Sapling z spending key
     if (key.size() >= 2 && key[0] == 'S' && key[1] == 'K') return true;       // Sprout z spending key
-    // Transparent WIF: base58, ~51-52 chars, common version prefixes.
-    if (key.size() >= 51 && key.size() <= 52 &&
-        (key[0] == '5' || key[0] == 'K' || key[0] == 'L' || key[0] == 'U')) return true;
+    // Transparent WIF: decode Base58Check and confirm it is actually a secret key — version byte plus
+    // a 32-byte key, optionally a compression flag (payload 33 or 34 bytes). This accepts BOTH the
+    // compressed ("U…") and uncompressed ("7…") mainnet forms and the testnet form, and rejects
+    // addresses / typos via the real checksum — the old length+first-char heuristic dropped the
+    // uncompressed mainnet key (which starts with '7', not one of 5/K/L/U).
+    std::vector<std::uint8_t> payload;
+    if (util::decodeBase58Check(key, payload) &&
+        (payload.size() == 33 || payload.size() == 34) &&
+        (payload[0] == 188 /* DragonX main/regtest SECRET_KEY */ ||
+         payload[0] == 128 /* DragonX testnet SECRET_KEY */)) {
+        return true;
+    }
     return false;
 }