feat: add multi-select to gallery

multi-select actions include:
- drag to board to move all to that board
- right click to add all to board or delete all

backend changes:
- add routes for changing board for list of image names, deleting list of images
- change image-specific routes to `images/i/{image_name}` to not clobber other routes (like `images/upload`, `images/delete`)
- subclass pydantic `BaseModel` as `BaseModelExcludeNull`, which excludes null values when calling `dict()` on the model. this fixes inconsistent types related to JSON parsing null values into `null` instead of `undefined`
- remove `board_id` from `remove_image_from_board`

frontend changes:
- multi-selection stuff uses `ImageDTO[]` as payloads, for dnd and other mutations. this gives us access to image `board_id`s when hitting routes, and enables efficient cache updates.
- consolidate change board and delete image modals to handle single and multiples
- board totals are now re-fetched on mutation and not kept in sync manually - was way too tedious to do this
- fixed warning about nested `<p>` elements
- closes #4088 , need to handle case when `autoAddBoardId` is `"none"`
- add option to show gallery image delete button on every gallery image

frontend refactors/organisation:
- make typegen script js instead of ts
- enable `noUncheckedIndexedAccess` to help avoid bugs when indexing into arrays, many small changes needed to satisfy TS after this
- move all image-related endpoints into `endpoints/images.ts`, its a big file now, but this fixes a number of circular dependency issues that were otherwise felt impossible to resolve

invokeai/app/util/model_exclude_null.py

@@ -0,0 +1,23 @@
+from typing import Any
+from pydantic import BaseModel
+
+
+"""
+We want to exclude null values from objects that make their way to the client.
+
+Unfortunately there is no built-in way to do this in pydantic, so we need to override the default
+dict method to do this.
+
+From https://github.com/tiangolo/fastapi/discussions/8882#discussioncomment-5154541
+"""
+
+
+class BaseModelExcludeNull(BaseModel):
+    def dict(self, *args, **kwargs) -> dict[str, Any]:
+        """
+        Override the default dict method to exclude None values in the response
+        """
+        kwargs.pop("exclude_none", None)
+        return super().dict(*args, exclude_none=True, **kwargs)
+
+    pass