Add multi-database data layer

Introduce aether-data-schema and driver-specific schema generation for Postgres, MySQL, and SQLite.

Split data backends, lifecycle, repositories, and gateway runtime integration across database drivers.

Verified with cargo fmt --all --check, cargo clippy --workspace --all-targets -- -D warnings, and cargo test --workspace.

crates/aether-data/schema/generated/sqlite/baseline/003_auth_config.sql

@@ -0,0 +1,75 @@
+-- Generated by aether-data-schema from schema/logical/*.toml.
+-- Do not edit generated files directly; edit logical schema or explicit overrides instead.
+
+CREATE TABLE IF NOT EXISTS system_configs (
+    id TEXT PRIMARY KEY NOT NULL,
+    key TEXT NOT NULL,
+    value TEXT NOT NULL,
+    description TEXT,
+    created_at INTEGER NOT NULL,
+    updated_at INTEGER NOT NULL,
+    UNIQUE (key)
+);
+
+CREATE TABLE IF NOT EXISTS auth_modules (
+    id TEXT PRIMARY KEY NOT NULL,
+    module_type TEXT NOT NULL,
+    enabled INTEGER NOT NULL DEFAULT 1,
+    config TEXT NOT NULL,
+    created_at INTEGER NOT NULL,
+    updated_at INTEGER NOT NULL,
+    UNIQUE (module_type)
+);
+
+CREATE TABLE IF NOT EXISTS oauth_providers (
+    provider_type TEXT PRIMARY KEY NOT NULL,
+    display_name TEXT NOT NULL,
+    client_id TEXT NOT NULL,
+    client_secret_encrypted TEXT,
+    authorization_url_override TEXT,
+    token_url_override TEXT,
+    userinfo_url_override TEXT,
+    scopes TEXT,
+    redirect_uri TEXT NOT NULL,
+    frontend_callback_url TEXT NOT NULL,
+    attribute_mapping TEXT,
+    extra_config TEXT,
+    is_enabled INTEGER NOT NULL DEFAULT 0,
+    created_at INTEGER NOT NULL,
+    updated_at INTEGER NOT NULL
+);
+
+CREATE TABLE IF NOT EXISTS ldap_configs (
+    id INTEGER PRIMARY KEY AUTOINCREMENT,
+    server_url TEXT NOT NULL,
+    bind_dn TEXT NOT NULL,
+    bind_password_encrypted TEXT,
+    base_dn TEXT NOT NULL,
+    user_search_filter TEXT NOT NULL DEFAULT '(uid={username})',
+    username_attr TEXT NOT NULL DEFAULT 'uid',
+    email_attr TEXT NOT NULL DEFAULT 'mail',
+    display_name_attr TEXT NOT NULL DEFAULT 'cn',
+    is_enabled INTEGER NOT NULL DEFAULT 0,
+    is_exclusive INTEGER NOT NULL DEFAULT 0,
+    use_starttls INTEGER NOT NULL DEFAULT 0,
+    connect_timeout INTEGER NOT NULL DEFAULT 10,
+    created_at INTEGER NOT NULL,
+    updated_at INTEGER NOT NULL
+);
+
+CREATE TABLE IF NOT EXISTS user_oauth_links (
+    id TEXT PRIMARY KEY NOT NULL,
+    user_id TEXT NOT NULL,
+    provider_type TEXT NOT NULL,
+    provider_user_id TEXT NOT NULL,
+    provider_username TEXT,
+    provider_email TEXT,
+    extra_data TEXT,
+    linked_at INTEGER NOT NULL,
+    last_login_at INTEGER,
+    UNIQUE (provider_type, provider_user_id),
+    UNIQUE (user_id, provider_type)
+);
+CREATE INDEX IF NOT EXISTS user_oauth_links_provider_type_idx ON user_oauth_links (provider_type);
+CREATE INDEX IF NOT EXISTS user_oauth_links_user_id_idx ON user_oauth_links (user_id);
+