feat(tui): load unlimited history and expose retention settings

[wendaining]

Changes

The history TUI previously truncated browsing and search results at 2,000 blocks. Load all matching records, following the issue's follow-up comment, while preserving explicit limits for other query callers.

Add a Retention category to recall config with editable output retention days (0 keeps output forever) and an Auto prune toggle. Changes use the existing atomic configuration store; cleanup runs when history opens and retains command records. Also prevent timestamp overflow for very large retention windows and document the controls in English and Chinese.

Validation

• Linux: cargo test passed (111 unit tests and 5 integration tests).
• Regression coverage includes more than 2,000 results across browsing, command/output searches, and short-term searches; retention input validation and persistence; large retention windows; and PTY editing, toggling, and alternate-screen restoration.
• cargo fmt, cargo clippy --all-targets, and git diff --check passed.
• macOS and Windows runtime validation remains for CI; the Linux run does not execute Windows ConPTY tests.

Closes #25