feat: implement pinned messages

- render pinned events on the chat top
- support scroll up for several pinned messages
- ask to unpin messages
- add button to pin message
- fix some null-safety issues
- fix the Linux database directly for debug builds

Signed-off-by: TheOneWithTheBraid <the-one@with-the-braid.cf>

assets/l10n/intl_de.arb

@@ -2723,5 +2723,7 @@
   "@bubbleSize": {
     "type": "text",
     "placeholders": {}
-  }
+  },
+  "pinMessage": "An Raum anheften",
+  "pinnedEventsError": "Angeheftete Nachrichten nicht gefunden"
 }

assets/l10n/intl_en.arb

@@ -2722,5 +2722,8 @@
       "sender": {},
       "reaction": {}
     }
-  }
+  },
+  "pinMessage": "Pin to room",
+  "pinnedEventsError": "Error loading pinned messages",
+  "confirmEventUnpin": "Are you sure to permanently unpin the event?"
 }