FEAT: Add configurable date format in settings

[andrinoff]

Is your feature request related to a problem? Date format hardcoded in code. Users in different locales want different formats (MM/DD vs DD/MM, 12h vs 24h).

Describe the solution you would like: Add date_format config option:

• "2006-01-02 15:04" (ISO)
• "01/02/2006 3:04 PM" (US)
• "02/01/2006 15:04" (EU)
• Custom Go time format string

Describe alternatives you have considered: Hardcoded format (current). Config allows personalization.

Additional context:

• Files: config/config.go, tui/inbox.go
• Use time.Format() with config value
• Provide presets in settings UI
• Complexity: Easy - config option + formatting

[Mohith32]

Hi! I'd like to work on this issue. Here's my planned approach:

Files to modify:

• config/config.go - Add a DateFormat field to the Config struct with json:"date_format,omitempty". Add preset constants (DateFormatISO, DateFormatUS, DateFormatEU) and a GetDateFormat() method that defaults to US format.
• tui/inbox.go - Update formatRelativeDate() to accept the configured date format and use it for absolute dates (older than 7 days) via time.Format().

Presets:

• "2006-01-02 15:04" (ISO)
• "01/02/2006 3:04 PM" (US)
• "02/01/2006 15:04" (EU)
• Any custom Go time format string

Users set it in their config.json:

{
  "date_format": "02/01/2006 15:04"
}

[andrinoff]

Hey, @Mohith32 ,

I like the approach, just let's make the configuration "DD/MM/YYYY HH:MM" instead of a specific date and time.