feat: responsive layout + Reminder Manager redesign

- Auto-collapse sidebar at <1536px (all laptops), expand at ≥1536px
- Responsive drawer/panel widths across Pipeline, Properties, MyListings, Anfragen, MatchDetail, AISearch
- Reminder Manager: dot+label priority badge, Fläche column removed, status only for non-active rows
- ReminderKpiBar: focal Überfällig card, three secondary KPIs
- ReminderDetailDrawer: Task Panel redesign — Finanzen removed, Notiz promoted, Pre-Market as inline badge, full create form
- useCreateReminder hook wired to reminderService.create with cache invalidation
- Mock data: contract-derived reminders (LEASE_EXPIRY, BREAK_OPTION, RENT_REVIEW, INSURANCE_RENEWAL, SCHATTENMARKT_RELEASE) now show auto-creation note in Verlauf

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/pages/demand/Pipeline.tsx

@@ -109,7 +109,7 @@ export default function Pipeline() {
               return (
                 <Box
                   key={stage.key}
-                  sx={{ minWidth: syncedSelected ? 190 : 230, maxWidth: syncedSelected ? 230 : 270, flexShrink: 0, display: 'flex', flexDirection: 'column' }}
+                  sx={{ minWidth: syncedSelected ? 170 : 200, maxWidth: syncedSelected ? 210 : 260, flexShrink: 0, display: 'flex', flexDirection: 'column' }}
                 >
                   <Box sx={{ py: 1, display: 'flex', alignItems: 'center', gap: 1 }}>
                     <Typography sx={{ fontWeight: 700, color: stage.color, fontSize: '0.8125rem' }}>