fix: resolve 6 TypeScript compilation errors

Fixed field name mismatches and generic type issues:
- database.ts: Changed camelCase to snake_case for key_password, private_key, public_key fields
- simple-db-ops.ts: Added explicit generic type parameters to DataCrypto method calls

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

src/backend/database/database.ts

@@ -678,7 +678,7 @@ app.post("/database/export", authenticateJWT, async (req, res) => {
           decrypted.authType,
           decrypted.password || null,
           decrypted.key || null,
-          decrypted.keyPassword || null,
+          decrypted.key_password || null,
           decrypted.keyType || null,
           decrypted.autostartPassword || null,
           decrypted.autostartKey || null,
@@ -721,9 +721,9 @@ app.post("/database/export", authenticateJWT, async (req, res) => {
           decrypted.username,
           decrypted.password || null,
           decrypted.key || null,
-          decrypted.privateKey || null,
-          decrypted.publicKey || null,
-          decrypted.keyPassword || null,
+          decrypted.private_key || null,
+          decrypted.public_key || null,
+          decrypted.key_password || null,
           decrypted.keyType || null,
           decrypted.detectedKeyType || null,
           decrypted.usageCount || 0,