fix(upgrade): add 5-minute timeout to pre-upgrade backup

[jorgehara]

Closes #446

Summary

• Adds 5-minute timeout to backup creation during upgrade
• Prevents indefinite hangs when backing up large config directories
• Fails gracefully with warning if timeout exceeded, upgrade proceeds

Changes

File	Change
\internal/backup/snapshot.go\	Add \context.Context\ parameter to \Create(), check cancellation between files
\internal/update/upgrade/executor.go\	Wrap backup call with 5-min timeout context
\internal/cli/run.go\	Add timeout to install/sync backup
\internal/components/uninstall/service.go\	Add timeout to uninstall backup
*_test.go\	Update all test mocks to accept context parameter

Test Plan

• All existing backup tests pass
• Project compiles without errors
• Manually verified timeout behavior (backup exceeds 5min → graceful failure)
• Pre-existing test failures unrelated to this change (verified on main branch)

Contributor Checklist

• Linked approved issue (fix(upgrade): pre-upgrade backup hangs indefinitely on large config directories #446)
• Added exactly one \ ype:bug\ label (will add after creation)
• Conventional commit format
• No Co-Authored-By trailers
• Solution benefits entire community (not just Cursor users)

[Alan-TheGentleman]

This is a useful bugfix, but the diff is too large for the stated behavior change.

Please add the required type:bug label and either split the context-plumbing churn from the timeout behavior or request a documented size:exception with a clear review boundary.