Make sure (most) queries avoid table scans.

I've exempted inserts (they never scan in the first place), queries on `event_sequence` (at most one row), and the coalesce()s used for event replay (for now; these are obviously a performance risk area and need addressing).

Method:

```
find .sqlx -name 'query-*.json' -exec jq -r '"explain query plan " + .query + ";"' {} + > explain.sql
```

Then go query by query through the resulting file.

1 files changed, 0 insertions, 44 deletions

diff --git a/.sqlx/query-2f4def5e6aa14d9bc4ca5db0d1f81953cd5f584b76ca59ece17d9ef2ce29ee9c.json b/.sqlx/query-2f4def5e6aa14d9bc4ca5db0d1f81953cd5f584b76ca59ece17d9ef2ce29ee9c.json
deleted file mode 100644
index c1da170..0000000
--- a/.sqlx/query-2f4def5e6aa14d9bc4ca5db0d1f81953cd5f584b76ca59ece17d9ef2ce29ee9c.json
+++ /dev/null
@@ -1,44 +0,0 @@
-{
-  "db_name": "SQLite",
-  "query": "\n                select\n                    id as \"id: Id\",\n                    display_name as \"display_name: String\",\n                    canonical_name as \"canonical_name: String\",\n                    created_sequence as \"created_sequence: Sequence\",\n                    created_at as \"created_at: DateTime\"\n                from login\n                    where coalesce(created_sequence <= $1, true)\n                    order by created_sequence\n            ",
-  "describe": {
-    "columns": [
-      {
-        "name": "id: Id",
-        "ordinal": 0,
-        "type_info": "Text"
-      },
-      {
-        "name": "display_name: String",
-        "ordinal": 1,
-        "type_info": "Text"
-      },
-      {
-        "name": "canonical_name: String",
-        "ordinal": 2,
-        "type_info": "Text"
-      },
-      {
-        "name": "created_sequence: Sequence",
-        "ordinal": 3,
-        "type_info": "Integer"
-      },
-      {
-        "name": "created_at: DateTime",
-        "ordinal": 4,
-        "type_info": "Text"
-      }
-    ],
-    "parameters": {
-      "Right": 1
-    },
-    "nullable": [
-      false,
-      false,
-      false,
-      false,
-      false
-    ]
-  },
-  "hash": "2f4def5e6aa14d9bc4ca5db0d1f81953cd5f584b76ca59ece17d9ef2ce29ee9c"
-}