ndb: add safemode so we don't instantly crash on bad dbs

Fixes: https://github.com/damus-io/damus/issues/1741

damus/ContentView.swift

@@ -602,7 +602,20 @@ struct ContentView: View {
 
     func connect() {
         // nostrdb
-        let ndb = try! Ndb()!
+        var mndb = Ndb()
+        if mndb == nil {
+            // try recovery
+            print("DB ISSUE! RECOVERING")
+            mndb = Ndb.safemode()
+
+            // out of space or something?? maybe we need a in-memory fallback
+            if mndb == nil {
+                notify(.logout)
+                return
+            }
+        }
+
+        guard let ndb = mndb else { return  }
 
         let pool = RelayPool(ndb: ndb)
         let model_cache = RelayModelCache()

damus/TestData.swift

@@ -64,7 +64,7 @@ var test_damus_state: DamusState = ({
     }
 
     print("opening \(tempDir!)")
-    let ndb = try! Ndb(path: tempDir)!
+    let ndb = Ndb(path: tempDir)!
     let our_pubkey = test_pubkey
     let pool = RelayPool(ndb: ndb)
     let settings = UserSettingsStore()

damus/Views/SaveKeysView.swift

@@ -10,7 +10,7 @@ import Security
 
 struct SaveKeysView: View {
     let account: CreateAccountModel
-    let pool: RelayPool = RelayPool(ndb: try! Ndb()!)
+    let pool: RelayPool = RelayPool(ndb: Ndb()!)
     @State var pub_copied: Bool = false
     @State var priv_copied: Bool = false
     @State var loading: Bool = false