feat(wallet): persist history and surface pending sends

Add an encrypted SQLite transaction history cache with cached tip metadata and
per-address shielded scan progress so startup and full refreshes avoid
re-scanning every z-address while still invalidating on wallet/address/rescan
changes.

Improve wallet history loading by paging transparent transactions, preserving
cached shielded and sent rows, keeping recent/unconfirmed activity visible, and
classifying mining-address receives. Show z_sendmany opid sends immediately in
History and Overview, pin pending rows through refreshes, and apply optimistic
address/balance debits until opids resolve.

Add timestamped RPC console tracing by source/method without logging params or
results, reduce redundant refresh/RPC calls, and cache Explorer recent block
summaries in SQLite.

Expand focused tests for transaction cache encryption, scan-progress
persistence/invalidation, history preservation, operation-status parsing,
pending send visibility, and Explorer/RPC refresh behavior.

src/data/transaction_history_cache.h

@@ -0,0 +1,90 @@
+#pragma once
+
+#include "wallet_state.h"
+
+#include <array>
+#include <cstdint>
+#include <ctime>
+#include <string>
+#include <unordered_map>
+#include <vector>
+
+struct sqlite3;
+
+namespace dragonx {
+namespace data {
+
+class TransactionHistoryCache {
+public:
+    struct LoadResult {
+        bool loaded = false;
+        bool invalidated = false;
+        int tipHeight = 0;
+        std::string tipHash;
+        std::time_t updatedAt = 0;
+        std::vector<TransactionInfo> transactions;
+        std::unordered_map<std::string, int> shieldedScanHeights;
+    };
+
+    TransactionHistoryCache();
+    explicit TransactionHistoryCache(std::string databasePath);
+    ~TransactionHistoryCache();
+
+    TransactionHistoryCache(const TransactionHistoryCache&) = delete;
+    TransactionHistoryCache& operator=(const TransactionHistoryCache&) = delete;
+
+    static std::string defaultDatabasePath();
+    static std::string walletIdentityFromAddresses(const std::vector<std::string>& shieldedAddresses,
+                                                   const std::vector<std::string>& transparentAddresses);
+    static std::string walletIdentityHash(const std::string& walletIdentity);
+
+    bool ensureOpen();
+    bool unlockWithPassphrase(const std::string& walletIdentity, const std::string& passphrase);
+    void lockKey();
+    bool hasKey() const { return key_ready_; }
+    bool isUnlockedFor(const std::string& walletIdentity) const;
+
+    LoadResult load(const std::string& walletIdentity,
+                    int currentTipHeight,
+                    const std::string& currentTipHash);
+    bool replace(const std::string& walletIdentity,
+                 int tipHeight,
+                 const std::string& tipHash,
+                 const std::vector<TransactionInfo>& transactions,
+                 std::time_t updatedAt,
+                 const std::unordered_map<std::string, int>& shieldedScanHeights = {});
+    void clearWallet(const std::string& walletIdentity);
+    int snapshotCount();
+
+private:
+    bool exec(const char* sql);
+    bool createSchema();
+    std::vector<unsigned char> getOrCreateSalt(const std::string& walletHash);
+    bool deriveKey(const std::string& passphrase,
+                   const std::vector<unsigned char>& salt);
+    bool encryptPayload(const std::string& walletHash,
+                        const std::string& plainText,
+                        std::vector<unsigned char>& nonce,
+                        std::vector<unsigned char>& cipherText) const;
+    bool decryptPayload(const std::string& walletHash,
+                        const std::vector<unsigned char>& nonce,
+                        const std::vector<unsigned char>& cipherText,
+                        std::string& plainText) const;
+    bool readSnapshot(const std::string& walletHash,
+                      int& tipHeight,
+                      std::string& tipHash,
+                      std::time_t& updatedAt,
+                      std::vector<unsigned char>& nonce,
+                      std::vector<unsigned char>& cipherText);
+    void clearWalletByHash(const std::string& walletHash);
+    void close();
+
+    sqlite3* db_ = nullptr;
+    std::string database_path_;
+    std::array<unsigned char, 32> key_{};
+    bool key_ready_ = false;
+    std::string unlocked_wallet_hash_;
+};
+
+} // namespace data
+} // namespace dragonx