chore: stop tracking vendor lib files (now restored via npm + esbuild)

Drops 1038 files from src/Yavsc.Org/wwwroot/lib/ — they remain
on disk and are now restored via 'npm install' at build time
(see package.json and esbuild.config.mjs).

Exception: jonthornton-Datepair is not on npm, the bundled
files are kept in wwwroot/lib/jonthornton-Datepair/ as static
assets.

Also extends .gitignore to ignore:
- node_modules/, build/, package-lock.json (esbuild toolchain)
- wwwroot/js/*.min.js (regenerated by 'npm run build:js')
- .Production.env (added explicitly, not matched by '.*.env'
  glob in some git versions)

This aligns themeok with the architecture already in place
on refac/js-bundle (commits ed7522c5, 196f4b0b, 292c0a2f on
that branch). The build artifacts were already present in
node_modules/ and build/ on disk; this commit only stops
tracking them.

Tested: dotnet test 11/11 green (no C# code touched).

src/Yavsc.Org/wwwroot/lib/microsoft/signalr/dist/esm/AccessTokenHttpClient.d.ts

@@ -1,11 +0,0 @@
-import { HttpClient, HttpRequest, HttpResponse } from "./HttpClient";
-/** @private */
-export declare class AccessTokenHttpClient extends HttpClient {
-    private _innerClient;
-    _accessToken: string | undefined;
-    _accessTokenFactory: (() => string | Promise<string>) | undefined;
-    constructor(innerClient: HttpClient, accessTokenFactory: (() => string | Promise<string>) | undefined);
-    send(request: HttpRequest): Promise<HttpResponse>;
-    private _setAuthorizationHeader;
-    getCookieString(url: string): string;
-}