use SQL's limit/offset pagination for nextIndex/maxCount requests (#185)

Instead of retrieving the entire list of items/characters/scores/etc. at once (and even store them in memory), use SQL's `LIMIT ... OFFSET ...` pagination so we only take what we need.

Currently only CHUNITHM uses this, but this will also affect maimai DX and O.N.G.E.K.I. once the PR is ready.

Also snuck in a fix for CHUNITHM/maimai DX's `GetUserRivalMusicApi` to respect the `userRivalMusicLevelList` sent by the client.

### How this works

Say we have a `GetUserCharacterApi` request:

```json
{
    "userId": 10000,
    "maxCount": 700,
    "nextIndex": 0
}
```

Instead of getting the entire character list from the database (which can be very large if the user force unlocked everything), add limit/offset to the query:

```python
select(character)
.where(character.c.user == user_id)
.order_by(character.c.id.asc())
.limit(max_count + 1)
.offset(next_index)
```

The query takes `maxCount + 1` items from the database to determine if there is more items than can be returned:

```python
rows = ...

if len(rows) > max_count:
    # return only max_count rows
    next_index += max_count
else:
    # return everything left
    next_index = -1
```

This has the benefit of not needing to load everything into memory (and also having to store server state, as seen in the [`SCORE_BUFFER` list](2274b42358/titles/chuni/base.py (L13)).)

Reviewed-on: Hay1tsme/artemis#185
Co-authored-by: beerpsi <beerpsi@duck.com>
Co-committed-by: beerpsi <beerpsi@duck.com>

titles/chuni/const.py

@@ -1,4 +1,4 @@
-from enum import Enum
+from enum import Enum, IntEnum
 
 
 class ChuniConstants:
@@ -81,12 +81,31 @@ class ChuniConstants:
         return cls.VERSION_NAMES[ver]
 
 
-class MapAreaConditionType(Enum):
-    UNLOCKED = 0
+class MapAreaConditionType(IntEnum):
+    """Condition types for the GetGameMapAreaConditionApi endpoint. Incomplete.
+
+    For the MAP_CLEARED/MAP_AREA_CLEARED/TROPHY_OBTAINED conditions, the conditionId
+    is the map/map area/trophy.
+
+    For the RANK_*/ALL_JUSTICE conditions, the conditionId is songId * 100 + difficultyId.
+    For example, Halcyon [ULTIMA] would be 173 * 100 + 4 = 17304.
+    """
+
+    ALWAYS_UNLOCKED = 0
+    
     MAP_CLEARED = 1
     MAP_AREA_CLEARED = 2
+    
     TROPHY_OBTAINED = 3
 
+    RANK_SSS = 19
+    RANK_SSP = 20
+    RANK_SS = 21
+    RANK_SP = 22
+    RANK_S = 23
+
+    ALL_JUSTICE = 28
+
 
 class MapAreaConditionLogicalOperator(Enum):
     AND = 1
@@ -102,11 +121,36 @@ class AvatarCategory(Enum):
     FRONT = 6
     BACK = 7
 
-class ItemKind(Enum):
+class ItemKind(IntEnum):
     NAMEPLATE = 1
+    
+    FRAME = 2
+    """
+    "Frame" is the background for the gauge/score/max combo display
+    shown during gameplay. This item cannot be equipped (as of LUMINOUS)
+    and is hardcoded to the current game's version.
+    """
+
     TROPHY = 3
+    SKILL = 4
+
     TICKET = 5
+    """A statue is also a ticket."""
+
     PRESENT = 6
+    MUSIC_UNLOCK = 7
     MAP_ICON = 8
     SYSTEM_VOICE = 9
-    AVATAR_ACCESSORY = 11
+    SYMBOL_CHAT = 10
+    AVATAR_ACCESSORY = 11
+
+    ULTIMA_UNLOCK = 12
+    """This only applies to ULTIMA difficulties that are *not* unlocked by
+    SS-ing EXPERT+MASTER.
+    """
+
+
+class FavoriteItemKind(IntEnum):
+    MUSIC = 1
+    RIVAL = 2
+    CHARACTER = 3