🔧 chore: create @manacore/shared-tsconfig and migrate 13 backends

- Create shared TypeScript config package with:
  - base.json: Common options (ES2021, skipLibCheck, etc.)
  - nestjs.json: NestJS backend config (decorators, commonjs)
  - sveltekit.json: SvelteKit web config
  - expo.json: Expo mobile config
  - astro.json: Astro landing config

- Migrate 13 NestJS backends to use shared config:
  calendar, chat, clock, contacts, nutriphi, picture, planta,
  presi, questions, skilltree, storage, todo, zitare

- Skip manadeck (uses nodenext module system)

Savings: ~280 LOC (13 backends × ~22 LOC each)

apps/zitare/apps/backend/tsconfig.json

@@ -1,25 +1,3 @@
 {
-	"compilerOptions": {
-		"module": "commonjs",
-		"moduleResolution": "node",
-		"declaration": true,
-		"removeComments": true,
-		"emitDecoratorMetadata": true,
-		"experimentalDecorators": true,
-		"allowSyntheticDefaultImports": true,
-		"target": "ES2021",
-		"sourceMap": true,
-		"outDir": "./dist",
-		"baseUrl": "./",
-		"rootDir": "./src",
-		"incremental": true,
-		"skipLibCheck": true,
-		"strictNullChecks": true,
-		"noImplicitAny": true,
-		"strictBindCallApply": true,
-		"forceConsistentCasingInFileNames": true,
-		"noFallthroughCasesInSwitch": true
-	},
-	"include": ["src/**/*"],
-	"exclude": ["node_modules", "dist"]
+	"extends": "@manacore/shared-tsconfig/nestjs"
 }