feat(springboard): add get_icon_state and set_icon_state methods (#63)

* feat(springboard): add get_icon_state method for reading home screen layout

Add get_icon_state() method to SpringBoardServicesClient that retrieves
the current home screen icon layout from iOS devices.

Features:
- Read complete home screen layout including icon positions and folders
- Support for optional formatVersion parameter
- Works on all iOS versions (tested on iOS 18.7.3)
- Comprehensive documentation with usage examples

Note: This PR intentionally does NOT include set_icon_state() as that
functionality is non-operational on iOS 18+ (see issue #62 for details).

Tested on:
- Device: iPhone 16,2 (iPhone 15 Pro)
- iOS: 18.7.3 (Build 22H217)

* feat(springboard): add set_icon_state method with date precision fix

- Implement set_icon_state() to modify home screen layout
- Implement set_icon_state_with_version() with format_version parameter
- Add truncate_dates_to_seconds() to convert nanosecond precision dates to second precision
- Fix iOS compatibility issue where high-precision dates were rejected
- Successfully tested on iOS 18.7.3 (previously believed to be restricted)
- Follows pymobiledevice3 implementation pattern

* refactor(utils): extract truncate_dates_to_seconds to utils::plist module

- Move date truncation logic from springboardservices to reusable utils::plist module
- Add comprehensive unit tests for date truncation functionality
- Add public API documentation for the utility function
- This makes the date normalization logic available for other services that may need it

* perf(springboard): normalize dates on read instead of write

- Move date truncation from set_icon_state to get_icon_state
- Eliminates unnecessary clone() operation in set_icon_state
- Better performance when setting icon state multiple times
- Cleaner API: data from get_icon_state is directly usable in set_icon_state
- Users don't need to worry about date precision issues

* refactor(springboard): address PR feedback - use Option<&str> and add error validation

- Change format_version parameter from Option<String> to Option<&str> for consistency
- Remove outdated iOS 18+ restriction comments since setIconState works on iOS 18+
- Add error validation to get_icon_state method similar to get_icon_pngdata
- Update documentation to reflect accurate iOS compatibility

* Fix cargo clippy warnings

* Fix clippy warnings in plist.rs

* Add springboard CLI commands

---------

Co-authored-by: Jackson Coxson <jkcoxson@gmail.com>

Cargo.lock

@@ -1782,9 +1782,9 @@ dependencies = [
 
 [[package]]
 name = "plist-macro"
-version = "0.1.0"
+version = "0.1.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "cb72007326fe20721ef27304fcf2d1bd5877b92d13dbd8df735fd33407e31c2a"
+checksum = "8888e02e251eba3258cc58fb79f0d8675c34b3428749e738562d58a0271bf035"
 dependencies = [
  "plist",
 ]