fix(mana/web): sprint 2 — auth-aware data layer + guest migration

- Single source of truth for the active user via data/current-user.ts;
  layout pushes authStore.user.id into it on every auth state change.
- Dexie creating-hook auto-stamps userId from getEffectiveUserId(); the
  updating-hook strips userId from modifications so records are
  effectively user-immutable after creation.
- BaseRecord gains an optional userId so module types inherit it without
  per-module declarations. All hardcoded 'guest'/'local' fallbacks in
  module type-converters and session timer stores are deleted; the dead
  userId field is removed from the public view types where it was
  unused (Task, Conversation, Template, Deck, Plant, Contact, etc.).
- New guest-migration.ts: on first authenticated session, walks every
  sync-tracked table, deletes guest-owned records and re-adds them so
  the creating-hook re-stamps with the real user id and produces fresh
  insert pending-changes with the full payload. Stale guest pending-
  changes are cleared up-front.
- Drive-by: root onMount now returns its cleanup synchronously; the
  previous async form silently dropped the cleanup callback.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

apps/mana/apps/web/src/lib/modules/chat/queries.ts

@@ -18,7 +18,6 @@ import type {
 export function toConversation(local: LocalConversation): Conversation {
 	return {
 		id: local.id,
-		userId: local.userId ?? 'guest',
 		modelId: local.modelId ?? '',
 		templateId: local.templateId ?? undefined,
 		spaceId: local.spaceId ?? undefined,
@@ -35,7 +34,6 @@ export function toConversation(local: LocalConversation): Conversation {
 export function toTemplate(local: LocalTemplate): Template {
 	return {
 		id: local.id,
-		userId: local.userId ?? 'guest',
 		name: local.name,
 		description: local.description || null,
 		systemPrompt: local.systemPrompt,

apps/mana/apps/web/src/lib/modules/chat/types.ts

@@ -36,7 +36,6 @@ export interface LocalTemplate extends BaseRecord {
 
 export interface Conversation {
 	id: string;
-	userId: string;
 	modelId: string;
 	templateId?: string;
 	spaceId?: string;
@@ -60,7 +59,6 @@ export interface Message {
 
 export interface Template {
 	id: string;
-	userId: string;
 	name: string;
 	description: string | null;
 	systemPrompt: string;