chore(db): remove 23 unused database methods (#22999)

Removes 22 database query methods with no callers outside generated code
and the dbauthz wrapper layer (~1,600 lines).

**Security keys (6)** — superseded by `cryptokeys` package:
`GetAppSecurityKey`, `UpsertAppSecurityKey`, `GetOAuthSigningKey`,
`UpsertOAuthSigningKey`, `GetCoordinatorResumeTokenSigningKey`,
`UpsertCoordinatorResumeTokenSigningKey`

**Superseded queries (4):**
- `GetProvisionerJobsByIDs` → `GetProvisionerJobsByIDsWithQueuePosition`
- `GetDeploymentDAUs` / `GetTemplateDAUs` →
`GetTemplateInsightsByInterval`
- `GetWorkspaceBuildParametersByBuildIDs` + its `GetAuthorized...`
variant → unused

**OAuth2 (2):**
`GetOAuth2ProviderAppByRegistrationToken`,
`UpdateOAuth2ProviderAppSecretByID`

**Chat (4)** — pre-wired with no callers:
`GetChatModelConfigByProviderAndModel`, `DeleteChatMessagesByChatID`,
`ListChatsByRootID`, `ListChildChatsByParentID`

**Other (6):**
`DeleteGitSSHKey`, `UpdateUserLinkedID`, `GetFileIDByTemplateVersionID`,
`GetTemplateVersionHasAITask`, `InsertUserGroupsByName`,
`RemoveUserFromAllGroups`

coderd/database/queries/chats.sql

@@ -5,12 +5,6 @@ WHERE id = @id OR root_chat_id = @id;
 -- name: UnarchiveChatByID :exec
 UPDATE chats SET archived = false, updated_at = NOW() WHERE id = @id::uuid;
 
--- name: DeleteChatMessagesByChatID :exec
-DELETE FROM
-    chat_messages
-WHERE
-    chat_id = @chat_id::uuid;
-
 -- name: DeleteChatMessagesAfterID :exec
 DELETE FROM
     chat_messages
@@ -141,26 +135,6 @@ LIMIT
     -- Default to 50 to prevent accidental excessively large queries.
     COALESCE(NULLIF(@limit_opt :: int, 0), 50);
 
--- name: ListChildChatsByParentID :many
-SELECT
-    *
-FROM
-    chats
-WHERE
-    parent_chat_id = @parent_chat_id::uuid
-ORDER BY
-    created_at ASC;
-
--- name: ListChatsByRootID :many
-SELECT
-    *
-FROM
-    chats
-WHERE
-    root_chat_id = @root_chat_id::uuid
-ORDER BY
-    created_at ASC;
-
 -- name: InsertChat :one
 INSERT INTO chats (
     owner_id,