fix: Resolve issues with --notification-split-by-container feature

[nicholas-fedor]

This PR fixes the --notification-split-by-container feature that was implemented in response to issue #720 but found to be non-functional during testing and reported in issue #771. The feature was not working properly in general, beyond the specific edge case mentioned in #771.

Some time was also allocated towards refactoring the root.go file, which is sorely needed to facilitate future maintainability of the project.

Key Changes

fix: notification split by container when no update is performed

• Modify runUpdatesWithNotifications to handle notification splitting in both report and log modes
• Add GetEntries() and SendFilteredEntries() methods to notifier interface
• Update all notifier implementations with new interface methods
• Remove entry reset in Shoutrrr notifier to preserve log batch across multiple sends

refactor: modularize root command and extract utility functions

• Move runUpdatesWithNotifications function to actions.RunUpdatesWithNotifications
• Extract HTTP API setup logic to internal/api package
• Create internal/config package for configuration management
• Move startup logging to internal/logging package
• Extract scheduling logic to internal/scheduling package
• Add utility functions for duration formatting to internal/util package
• Update all import statements and package references
• Add comprehensive documentation and inline comments

Technical Details

Notification Splitting Implementation

// Report mode: Individual SingleContainerReport instances per updated container
// Log mode: Filtered logrus entries by container name
if notificationSplitByContainer && len(result.Updated()) > 0 {
    for _, updatedContainer := range result.Updated() {
        singleReport := &SingleContainerReport{
            UpdatedReports: []types.ContainerReport{updatedContainer},
            // ... include session context
        }
        notifier.SendNotification(singleReport)
    }
}

Package Structure Changes

internal/
├── actions/     # Update execution logic
├── api/         # HTTP API orchestration  
├── config/      # Configuration management
├── logging/     # Startup logging
├── scheduling/  # Cron scheduling
└── util/        # Utility functions

[codecov]

Codecov Report

❌ Patch coverage is 75.51020% with 120 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
internal/actions/actions.go	71.02%	30 Missing and 1 partial ⚠️
internal/scheduling/scheduling.go	80.51%	13 Missing and 2 partials ⚠️
pkg/session/report.go	63.41%	15 Missing ⚠️
internal/api/api.go	72.54%	12 Missing and 2 partials ⚠️
internal/logging/startup.go	88.46%	8 Missing and 4 partials ⚠️
pkg/notifications/shoutrrr.go	0.00%	10 Missing ⚠️
pkg/api/api.go	69.56%	4 Missing and 3 partials ⚠️
pkg/notifications/email.go	0.00%	4 Missing ⚠️
pkg/notifications/gotify.go	0.00%	4 Missing ⚠️
pkg/notifications/msteams.go	0.00%	4 Missing ⚠️
... and 1 more

❌ Your changes status has failed because you have indirect coverage changes. Learn more about Unexpected Coverage Changes and reasons for indirect coverage changes.

@@            Coverage Diff             @@
##             main     #775      +/-   ##
==========================================
+ Coverage   73.57%   73.81%   +0.23%     
==========================================
  Files          45       49       +4     
  Lines        6482     6923     +441     
==========================================
+ Hits         4769     5110     +341     
- Misses       1556     1643      +87     
- Partials      157      170      +13     

Files with missing lines	Coverage Δ
internal/util/util.go	100.00% <100.00%> (ø)
pkg/api/update/update.go	93.68% <100.00%> (+0.91%)	⬆️
pkg/notifications/email.go	81.13% <0.00%> (-3.19%)	⬇️
pkg/notifications/gotify.go	71.26% <0.00%> (-3.44%)	⬇️
pkg/notifications/msteams.go	60.00% <0.00%> (-5.22%)	⬇️
pkg/notifications/slack.go	89.15% <0.00%> (-4.52%)	⬇️
pkg/api/api.go	93.96% <69.56%> (-6.04%)	⬇️
pkg/notifications/shoutrrr.go	76.88% <0.00%> (-6.17%)	⬇️
internal/logging/startup.go	88.46% <88.46%> (ø)
internal/api/api.go	72.54% <72.54%> (ø)
... and 3 more

... and 1 file with indirect coverage changes

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