feat: add @manacore/shared-links for cross-app record linking

New shared package enabling bidirectional links between records across
apps (e.g. todo→calendar, task→file). Each link creates a forward+reverse
pair sharing a pairId for efficient queries from both sides. Stored in
dedicated IndexedDB (manacore-links), synced via mana-sync.

Includes: types, store, mutations, reactive queries, cached display data
resolvers, ManaLinkBadge and ManaLinkList UI components.

Integrates into Todo app as first consumer — link store initialized in
layout, ManaLinkList rendered in TaskEditModal.

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

packages/shared-links/tsconfig.json

@@ -0,0 +1,19 @@
+{
+	"compilerOptions": {
+		"target": "ES2022",
+		"module": "ES2022",
+		"moduleResolution": "bundler",
+		"strict": true,
+		"esModuleInterop": true,
+		"skipLibCheck": true,
+		"forceConsistentCasingInFileNames": true,
+		"resolveJsonModule": true,
+		"isolatedModules": true,
+		"declaration": true,
+		"declarationMap": true,
+		"sourceMap": true,
+		"outDir": "dist",
+		"types": ["svelte"]
+	},
+	"include": ["src/**/*"]
+}