fix: address potential bugs found in code review

[yitsushi]

Bug fixes:

• import: pass empty namespace to AddNamespace so accounts from new namespaces are not mistakenly treated as conflicts, causing spurious overwrite prompts
• set-length: validate ParseUint result and re-prompt on non-numeric input instead of silently storing length=0
• cmd: propagate terminal read errors from all askFor* helpers to prevent infinite loops on EOF/pipe close (add_token, set_length, set_prefix, rename, instant)
• generateCode: return error instead of printing to stdout so callers can surface failures rather than displaying an empty token
• CheckPasswordConfirm: use crypto/subtle.ConstantTimeCompare to avoid timing side-channel

Refactoring for testability:

• terminal: extract Terminal interface; New() returns *ConcreteTerminal
• storage: add PasswordProvider interface + StaticPasswordProvider; FileBackend accepts provider via WithPasswordProvider option
• cmd: extract execute*/askFor* functions with injected Terminal and Storage dependencies; add prepareStorage helper

Linter:

• replace deprecated wsl with wsl_v5, gomodguard with gomodguard_v2
• fix all noinlineerr and wsl_v5 violations; update quality-check action

Tests (overall coverage 22% → 63%):

• internal/cmd: add_token, change_password, delete, dump, error types, generate, import, list, rename, set_length, set_prefix, update
• internal/security/algo: SHA1/SHA256/SHA512/Default Hasher (0% → 100%)
• internal/security: OTPError.Error (97% → 100%)
• internal/storage: error types, SetPassword, acquirePassword branches

[Copilot]

Pull request overview

This PR addresses several CLI/storage correctness issues (password handling, token generation error propagation, input parsing) and refactors terminal/storage/cmd code to improve testability, adding substantial new unit test coverage and updating lint/CI configuration.

Changes:

• Refactors command handlers to inject Terminal and Storage dependencies and adds PasswordProvider support in storage to remove terminal I/O from the backend.
• Improves error handling in user-input helpers and token generation (propagating terminal read errors; returning errors from generateCode).
• Adds/expands test suites across internal/cmd, internal/security, and internal/storage; updates golangci-lint configuration and CI workflow.

Reviewed changes

Copilot reviewed 41 out of 41 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
main.go	Minor error-handling refactor for lint compliance.
internal/terminal/terminal.go	Introduces Terminal interface and ConcreteTerminal implementation.
internal/storage/password.go	Adds PasswordProvider abstraction and static provider for tests.
internal/storage/filebackend.go	Injects password prompting via provider; refactors control flow for error handling.
internal/storage/filebackend_test.go	Updates tests for password provider injection; adds new password acquisition tests.
internal/storage/error_test.go	Adds coverage for storage error message formatting.
internal/security/check_password_confirm.go	Switches to constant-time compare for password confirmation.
internal/security/error_test.go	Adds coverage for security error message formatting.
internal/security/algo/algo_test.go	Adds coverage for hasher constructors.
internal/cmd/*.go	Refactors commands into execute*/askFor* helpers with dependency injection and improved error propagation.
internal/cmd/*_test.go	Adds new unit tests for refactored command logic.
go.mod	Updates declared Go version/tooling dependencies.
.golangci.yml	Updates linter configuration (disabling deprecated linters and adding wsl_v5 settings).
.github/workflows/quality-check.yaml	Updates CI Go version and golangci-lint action version.

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