refactor(version): centralize Homarr version in @homarr/version package

Replace fragile deep-relative 'package.json' imports across the monorepo
with a single source of truth: the new @homarr/version leaf package reads
the version once from the root package.json and exports it as VERSION.

Consumers now import by package name incl. the new User-Agent header in
fetchWithTrustedCertificatesAsync (packages/core):
  - core, api (info router), analytics, request-handler (update checker)
This also removes all manually-maintained relative version imports.

packages/api/src/router/info.ts

@@ -1,6 +1,7 @@
 import z from "zod/v4";
 
-import packageJson from "../../../../package.json";
+import { VERSION } from "@homarr/version";
+
 import { createTRPCRouter, isDemoMode, isDemoReadOnly, publicProcedure, protectedProcedure } from "../trpc";
 
 export const infoRouter = createTRPCRouter({
@@ -16,7 +17,7 @@ export const infoRouter = createTRPCRouter({
     })
     .query(() => {
       return {
-        version: packageJson.version,
+        version: VERSION,
       };
     }),
   isDemoMode: publicProcedure.query(() => isDemoMode),