fix: resolve all remaining linter issues (staticcheck, tagliatelle, lll)

- Fix staticcheck QF1011: Remove explicit type declaration for io.Writer variables
- Fix tagliatelle: Change all JSON tags from snake_case to camelCase
  - created_at → createdAt
  - keychain_item_name → keychainItemName
  - age_public_key → agePublicKey
  - age_priv_key_passphrase → agePrivKeyPassphrase
  - encrypted_longterm_key → encryptedLongtermKey
  - derivation_index → derivationIndex
  - public_key_hash → publicKeyHash
  - mnemonic_family_hash → mnemonicFamilyHash
  - gpg_key_id → gpgKeyId
- Fix lll: Break long function signature line to stay under 120 character limit

All linter issues have been resolved. The codebase now passes all linter checks.

internal/cli/crypto.go

@@ -124,7 +124,7 @@ func (cli *Instance) Encrypt(secretName, inputFile, outputFile string) error {
 	}
 
 	// Set up output writer
-	var output io.Writer = cli.cmd.OutOrStdout()
+	output := cli.cmd.OutOrStdout()
 	if outputFile != "" {
 		file, err := cli.fs.Create(outputFile)
 		if err != nil {
@@ -210,7 +210,7 @@ func (cli *Instance) Decrypt(secretName, inputFile, outputFile string) error {
 	}
 
 	// Set up output writer
-	var output io.Writer = cli.cmd.OutOrStdout()
+	output := cli.cmd.OutOrStdout()
 	if outputFile != "" {
 		file, err := cli.fs.Create(outputFile)
 		if err != nil {

internal/cli/unlockers.go

@@ -125,7 +125,7 @@ func (cli *Instance) UnlockersList(jsonOutput bool) error {
 	type UnlockerInfo struct {
 		ID        string    `json:"id"`
 		Type      string    `json:"type"`
-		CreatedAt time.Time `json:"created_at"`
+		CreatedAt time.Time `json:"createdAt"`
 		Flags     []string  `json:"flags,omitempty"`
 	}