i18n: Add 29 missing translation keys (DE + EN) and fix 19 hardcoded strings
Added missing i18n keys:
- action.upload, label.selected, student_portal.daily_inspiration
- auth.* (back_to_login, cancel, forgot_check_inbox, forgot_email_sent,
forgot_password_desc, password_weak/fair/good/strong, send_reset_link)
- attendance.daily_timeline, competition.unlimited
- date.* (jan through dec - short month names)
- drawing.bg_type, drawing.canvas_label
Fixed 19 hardcoded English strings:
- admin/compliance-overview: 5 strings (dashboard title, status, policies, log)
- admin/exam-proctoring: 3 strings (proctoring, sessions)
- admin/signage: 1 string (emergency signage)
- compliance-wizard: 3 strings (retention periods, checklist, complete)
- dashboard-customizer: 1 string (add widget)
- data-import-export: 2 strings (best practices, export regularly)
- district-management: 1 string (access denied)
- exam-session-monitor: 1 string (exam mode active)
- professional-calendar: 1 string (fixed 'Create Neues Ereignis' typo)
- ui/sidebar: 1 string (toggle sidebar)
Z User
333f3e9466