BUG: Date parsing fails for non-UTC timezones

[andrinoff]

Describe the bug: Email date parsing may fail or show incorrect times for non-UTC timezones. No timezone normalization.

To reproduce:

1. Receive email with Date header in non-UTC timezone
2. Display shows wrong time or parse error
3. Sorting by date may be incorrect

Expected behavior: Parse all RFC 5322 timezone formats. Convert to local time for display. Handle parsing errors gracefully.

Additional context:

• File: fetcher/fetcher.go or date parsing code
• Use time.Parse() with RFC1123Z layout
• Fall back to multiple formats if first fails
• Severity: Medium - data display bug
• Complexity: Easy - proper time.Parse usage