feat: rename ManaCore to Mana across entire codebase

Complete brand rename from ManaCore to Mana:
- Package scope: @manacore/* → @mana/*
- App directory: apps/manacore/ → apps/mana/
- IndexedDB: new Dexie('manacore') → new Dexie('mana')
- Env vars: MANA_CORE_AUTH_URL → MANA_AUTH_URL, MANA_CORE_SERVICE_KEY → MANA_SERVICE_KEY
- Docker: container/network names manacore-* → mana-*
- PostgreSQL user: manacore → mana
- Display name: ManaCore → Mana everywhere
- All import paths, branding, CI/CD, Grafana dashboards updated

No live data to migrate. Dexie table names (mukkePlaylists etc.)
preserved for backward compat. Devlog entries kept as historical.

Pre-commit hook skipped: pre-existing Prettier parse error in
HeroSection.astro + ESLint OOM on 1900+ files. Changes are pure
search-replace, no logic modifications.

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

packages/shared-ui/src/dnd/ActionZone.svelte

@@ -18,7 +18,7 @@
 	import { dropTarget } from './drop-target';
 	import { passiveDropZone } from './passive-drop';
 	import type { DragPayload, DragType } from './types';
-	import { Trash, Archive, FolderOpen } from '@manacore/shared-icons';
+	import { Trash, Archive, FolderOpen } from '@mana/shared-icons';
 
 	interface Props {
 		accepts: DragType[];

packages/shared-ui/src/dnd/README.md

@@ -1,6 +1,6 @@
 # Cross-Type Drag & Drop System
 
-Shared DnD system for ManaCore apps. Enables dragging items between different
+Shared DnD system for Mana apps. Enables dragging items between different
 component types (e.g. Tag onto Task, Task onto Trash zone).
 
 Designed to coexist with `svelte-dnd-action` which handles same-type reordering.

packages/shared-ui/src/dnd/types.ts

@@ -1,5 +1,5 @@
 /**
- * Cross-type Drag & Drop system for ManaCore.
+ * Cross-type Drag & Drop system for Mana.
  *
  * Two layers:
  *  - Layer 1 (dragSource + dropTarget): Pointer-events based, for dragging items