feat: add store push --force

This will

1. Wipe the remote store
2. Upload all of the local store to remote

Imagine the scenario where you end up with some mixed keys locally :(

You confirm this with

```
atuin store verify
```

You then fix it locally with

```
atuin store purge
```

Ensure that your local changes are reflected remotely with

```
atuin store push --force
```

and then (another PR, coming soon), update all other hosts with

```
atuin store pull --force
```

atuin-server-postgres/src/lib.rs

@@ -133,6 +133,19 @@ impl Database for Postgres {
         Ok(res.0 as i64)
     }
 
+    async fn delete_store(&self, user: &User) -> DbResult<()> {
+        sqlx::query(
+            "delete from store
+            where user_id = $1",
+        )
+        .bind(user.id)
+        .execute(&self.pool)
+        .await
+        .map_err(fix_error)?;
+
+        Ok(())
+    }
+
     async fn delete_history(&self, user: &User, id: String) -> DbResult<()> {
         sqlx::query(
             "update history