chore: extract shared tsconfig, move display-status to core, add i18n tests

- Add `@sofa/tsconfig` package with a shared `base.json` (target, lib, strict, moduleResolution, etc.) and migrate all packages/apps to `"extends": "@sofa/tsconfig/base.json"` to eliminate duplicated compiler options
- Move `display-status.ts` (and its `DisplayStatus` type + `getDisplayStatus` fn) from `@sofa/api` to `@sofa/core`; remove the `./display-status` export from `@sofa/api` and update all import sites in `discovery.ts` and `tracking.ts`
- Add `packages/core/test/display-status.test.ts`: 15 tests covering `ONGOING_TMDB_STATUSES` and all `getDisplayStatus` branches (movie, TV watchlist/in_progress/caught_up/completed, edge cases)
- Add `packages/i18n/vitest.config.ts` and two new test files: `date-buckets.test.ts` and `format.test.ts` covering date bucketing and locale formatting utilities

packages/core/package.json

@@ -11,6 +11,7 @@
     "./credits": "./src/credits.ts",
     "./cron": "./src/cron.ts",
     "./discovery": "./src/discovery.ts",
+    "./display-status": "./src/display-status.ts",
     "./export": "./src/export.ts",
     "./image-cache": "./src/image-cache.ts",
     "./imports": "./src/imports/index.ts",
@@ -49,6 +50,7 @@
     "zod": "catalog:"
   },
   "devDependencies": {
+    "@sofa/tsconfig": "workspace:*",
     "@types/adm-zip": "0.5.8",
     "@types/bun": "catalog:",
     "typescript": "catalog:",