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/cjs/DefaultHttpClient.js

@@ -1,45 +0,0 @@
-"use strict";
-// Licensed to the .NET Foundation under one or more agreements.
-// The .NET Foundation licenses this file to you under the MIT license.
-Object.defineProperty(exports, "__esModule", { value: true });
-exports.DefaultHttpClient = void 0;
-const Errors_1 = require("./Errors");
-const FetchHttpClient_1 = require("./FetchHttpClient");
-const HttpClient_1 = require("./HttpClient");
-const Utils_1 = require("./Utils");
-const XhrHttpClient_1 = require("./XhrHttpClient");
-/** Default implementation of {@link @microsoft/signalr.HttpClient}. */
-class DefaultHttpClient extends HttpClient_1.HttpClient {
-    /** Creates a new instance of the {@link @microsoft/signalr.DefaultHttpClient}, using the provided {@link @microsoft/signalr.ILogger} to log messages. */
-    constructor(logger) {
-        super();
-        if (typeof fetch !== "undefined" || Utils_1.Platform.isNode) {
-            this._httpClient = new FetchHttpClient_1.FetchHttpClient(logger);
-        }
-        else if (typeof XMLHttpRequest !== "undefined") {
-            this._httpClient = new XhrHttpClient_1.XhrHttpClient(logger);
-        }
-        else {
-            throw new Error("No usable HttpClient found.");
-        }
-    }
-    /** @inheritDoc */
-    send(request) {
-        // Check that abort was not signaled before calling send
-        if (request.abortSignal && request.abortSignal.aborted) {
-            return Promise.reject(new Errors_1.AbortError());
-        }
-        if (!request.method) {
-            return Promise.reject(new Error("No method defined."));
-        }
-        if (!request.url) {
-            return Promise.reject(new Error("No url defined."));
-        }
-        return this._httpClient.send(request);
-    }
-    getCookieString(url) {
-        return this._httpClient.getCookieString(url);
-    }
-}
-exports.DefaultHttpClient = DefaultHttpClient;
-//# sourceMappingURL=DefaultHttpClient.js.map