feat(ui): add configurable input panel max rows and horizontal scrolling

- Introduce `ui.input_max_rows` (default 5) to control how many rows the input panel expands before scrolling.
- Bump `CONFIG_SCHEMA_VERSION` to **1.2.0** and update migration documentation.
- Update `configuration.md` and migration guide to describe the new setting.
- Adjust TUI height calculation to respect `input_max_rows` and add horizontal scrolling support for long lines.
- Add `unicode-segmentation` dependency for proper grapheme handling.

crates/owlen-tui/Cargo.toml

@@ -18,6 +18,7 @@ crossterm = { workspace = true }
 tui-textarea = { workspace = true }
 textwrap = { workspace = true }
 unicode-width = "0.1"
+unicode-segmentation = "1.11"
 async-trait = "0.1"
 
 # Async runtime