characters: part 1 (schema, routes, API) (#1255)

- API first draft is done
- Schema is not quite done
- Queries obviously not ready

_database/sql/migrations_squashed/characters/characters.sql

@@ -0,0 +1,60 @@
+-- NB: This is a manually squashed view of all the CREATE and ALTER statements,
+-- with comments attached to the fields for centralized documentation.
+
+-- noinspection SqlDialectInspectionForFile
+-- noinspection SqlNoDataSourceInspectionForFile
+-- noinspection SqlResolveForFile
+
+-- Characters are reusable entities that can be referenced in video/image generations.
+-- A character is created from one or more reference images and registered with third-party
+-- systems (e.g. Kinovi/Seedance) that support character-based generation.
+CREATE TABLE characters (
+  -- Not used for anything except replication.
+  id BIGINT(20) NOT NULL AUTO_INCREMENT,
+
+  -- Effective "primary key" (PUBLIC)
+  token VARCHAR(32) NOT NULL,
+
+  -- Whether the character has been fully created and is available for use.
+  -- A character may exist in the database before its creation job completes.
+  is_active BOOLEAN NOT NULL DEFAULT false,
+
+  -- ========== CHARACTER DETAILS ==========
+
+  -- Display name for the character.
+  name VARCHAR(255) NOT NULL,
+
+  -- Optional description of the character.
+  maybe_description VARCHAR(512) DEFAULT NULL,
+
+  -- ========== MEDIA ==========
+
+  -- Avatar image (small/thumbnail).
+  maybe_avatar_media_token VARCHAR(32) DEFAULT NULL,
+
+  -- Full-size reference image.
+  maybe_full_image_media_token VARCHAR(32) DEFAULT NULL,
+
+  -- ========== CREATOR ==========
+
+  -- The user who created this character.
+  maybe_creator_user_token VARCHAR(32) DEFAULT NULL,
+
+  -- For abuse tracking.
+  creator_ip_address VARCHAR(40) NOT NULL,
+
+  -- ========== TIMESTAMPS ==========
+
+  created_at TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP,
+  updated_at TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
+  deleted_at TIMESTAMP DEFAULT NULL,
+
+  -- ========== INDICES ==========
+
+  PRIMARY KEY (id),
+  UNIQUE KEY (token),
+  KEY index_maybe_creator_user_token (maybe_creator_user_token),
+  KEY index_is_active (is_active),
+  KEY index_created_at (created_at)
+
+) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_bin;