fix: notification list HTTP 500 and add --all flag (#109)

[q-soriarty]

Summary

Closes #109

Root cause

Copia/Gitea returns HTTP 500 on GET /api/v1/notifications without any query parameters. Adding ?page=1 works around this server-side bug.

Additional fix

Added --all flag to show both read and unread notifications (passes ?all=true to API). Without this flag, only unread notifications are shown (Gitea default).

Investigation

GET /notifications           → 500
GET /notifications?page=1    → 200 (unread only)
GET /notifications?page=1&all=true → 200 (all notifications)

Test plan

• TestListRun_Success — list unread notifications
• TestListRun_Empty — empty list message
• TestListRun_AllFlag — --all shows read notifications
• All existing tests pass