Added suspension detection to filesync client, to restart connection

[guydols]

This pull request introduces support for detecting system suspend and resume events in GUI mode, allowing the filesync client to immediately reconnect after a system resume. The main addition is a new SuspendDetector utility, which is integrated into the GUI manager's session loop. This improves user experience by minimizing sync delays after a laptop or system wakes up from sleep. The change also includes basic tests for the new detector.

Suspend/resume detection feature:

• Added a new SuspendDetector utility (crates/filesync/src/suspend_detector.rs) that detects system suspend/resume by comparing wall-clock time with system uptime. On Linux, it reads /proc/uptime; on other platforms, it returns an unsupported error. ([crates/filesync/src/suspend_detector.rsR1-R71](https://github.com/guydols/ByteHive/pull/16/files#diff-e854a36d80dc4cdaf7f9cca2c9f03d1c25719e7e10b5d06b974b6ba3844e5aa0R1-R71))
• Integrated SuspendDetector into the GUI manager's session loop (crates/filesync/src/gui/manager.rs) to monitor for resume events and trigger immediate reconnection and user notification when a resume is detected. ([[1]](https://github.com/guydols/ByteHive/pull/16/files#diff-c6988c71cce54d886165a6e24dbe5234246e9ea011093c216a7783b138583b12R5), [[2]](https://github.com/guydols/ByteHive/pull/16/files#diff-c6988c71cce54d886165a6e24dbe5234246e9ea011093c216a7783b138583b12R86-R95), [[3]](https://github.com/guydols/ByteHive/pull/16/files#diff-c6988c71cce54d886165a6e24dbe5234246e9ea011093c216a7783b138583b12L145-R150))
• Documented the new suspend/resume detection feature in the README for GUI mode. ([crates/filesync/README.mdR343-R344](https://github.com/guydols/ByteHive/pull/16/files#diff-0be06c3d53c35473f47aad38f0a1bbebc7578e8e099cb380428a3ec360002a84R343-R344))

Testing and module organization:

• Added basic tests for SuspendDetector to ensure it initializes, implements Default, and its main method does not panic during normal operation (crates/filesync/tests/test_suspend_detector.rs). ([crates/filesync/tests/test_suspend_detector.rsR1-R27](https://github.com/guydols/ByteHive/pull/16/files#diff-2e52b2f7b05be8af788583df441bbb9efe076aac8f58912be15d747a4678746aR1-R27))
• Registered the new suspend_detector module in the crate root (crates/filesync/src/lib.rs). ([crates/filesync/src/lib.rsR11](https://github.com/guydols/ByteHive/pull/16/files#diff-6de8e376aa17b37bb20763deed1e531218c6af89ad8e01571e55d27bc74f3b43R11))