feat(config): support *_MB env vars for upload size limits

- Add `applyMegabytesOrBytesEnv` to accept size settings in either bytes or MB
- Prefer `*_BYTES` when set, otherwise convert `*_MB` to bytes with overflow guard
- Add coverage for MB-based environment overrides
- Introduce `static/js/upload-popups.js` to lazy-load and cache popup templatesfeat(config): support *_MB env vars for upload size limits

- Add `applyMegabytesOrBytesEnv` to accept size settings in either bytes or MB
- Prefer `*_BYTES` when set, otherwise convert `*_MB` to bytes with overflow guard
- Add coverage for MB-based environment overrides
- Introduce `static/js/upload-popups.js` to lazy-load and cache popup templates

static/js/upload-popups.js

@@ -0,0 +1,36 @@
+window.WBPopups = (() => {
+    const cache = new Map();
+    const docs = {
+        cli: { title: "CLI Guide", template: "cli" },
+        faq: { title: "Help & FAQ", template: "faq" },
+        dailyQuota: { title: "Upload limits", template: "upload-limits" },
+        about: { title: "About WarpBox", template: "about", about: true },
+        examples: { title: "Examples", template: "examples" },
+    };
+
+    async function loadTemplate(name) {
+        if (cache.has(name)) return cache.get(name);
+        const response = await fetch(`/static/popups/${name}.html`, { credentials: "same-origin" });
+        if (!response.ok) throw new Error(`Could not load popup template: ${name}`);
+        const template = await response.text();
+        cache.set(name, template);
+        return template;
+    }
+
+    async function renderTemplate(name, data = {}) {
+        const template = await loadTemplate(name);
+        return window.WBUtils.renderTemplate(template, data);
+    }
+
+    async function renderDoc(name, data = {}) {
+        const doc = docs[name];
+        if (!doc) return null;
+        return {
+            title: doc.title,
+            about: Boolean(doc.about),
+            html: await renderTemplate(doc.template, data),
+        };
+    }
+
+    return { renderTemplate, renderDoc };
+})();