Restructure frontend into templates/ and static/

- Move index.html → templates/index.html (Jinja2, uses url_for)
- Extract CSS → static/css/app.css
- Split JS into static/js/: utils.js, dashboard.js, shares.js,
  quotas.js, users.js, main.js
- Switch app.py from send_file to render_template

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

static/js/quotas.js

@@ -0,0 +1,70 @@
+let _qCtx = null;
+
+function openQuotaModal(type, name, path, validUsers) {
+    _qCtx = { type, name, path, users: validUsers ? validUsers.split(/[\s,]+/).filter(Boolean) : [] };
+    document.getElementById('quotaModalTitle').textContent =
+        'Quota — ' + (type === 'smb' ? esc(name) : esc(path));
+
+    let body = '';
+    if (type === 'smb' && _qCtx.users.length > 0) {
+        body = _qCtx.users.map(u => `
+            <div class="mb-3">
+                <label class="form-label" style="color:var(--muted); font-size:.85rem">${esc(u)}</label>
+                <div class="input-group">
+                    <input type="number" class="form-control quota-inp" data-user="${esc(u)}" placeholder="GB" min="1">
+                    <span class="input-group-text">GB</span>
+                </div>
+            </div>`).join('');
+    } else {
+        const note = type === 'nfs'
+            ? `<p class="mb-3" style="color:var(--muted); font-size:.87rem">Path: <code>${esc(path)}</code></p>`
+            : `<p class="mb-3" style="color:var(--muted); font-size:.87rem">No valid users on this share — enter a username manually.</p>`;
+        body = note + `
+            <div class="mb-3">
+                <label class="form-label" style="color:var(--muted); font-size:.85rem">Username</label>
+                <input type="text" id="qManualUser" class="form-control" placeholder="username">
+            </div>
+            <div class="mb-3">
+                <label class="form-label" style="color:var(--muted); font-size:.85rem">Quota</label>
+                <div class="input-group">
+                    <input type="number" id="qManualGB" class="form-control" placeholder="GB" min="1">
+                    <span class="input-group-text">GB</span>
+                </div>
+            </div>`;
+    }
+
+    document.getElementById('quotaModalBody').innerHTML = body;
+    new bootstrap.Modal(document.getElementById('quotaModal')).show();
+}
+
+async function submitQuota() {
+    if (!_qCtx) return;
+    const calls = [];
+
+    if (_qCtx.type === 'smb' && _qCtx.users.length > 0) {
+        for (const inp of document.querySelectorAll('.quota-inp')) {
+            const gb = parseInt(inp.value);
+            if (!gb || gb <= 0) continue;
+            calls.push({ type: 'smb', user: inp.dataset.user, quota: gb });
+        }
+    } else {
+        const user = document.getElementById('qManualUser')?.value.trim();
+        const gb = parseInt(document.getElementById('qManualGB')?.value);
+        if (!user) return showToast('Username is required.', 'danger');
+        if (!gb || gb <= 0) return showToast('Quota must be a positive number.', 'danger');
+        calls.push({ type: _qCtx.type, user, path: _qCtx.path, quota: gb });
+    }
+
+    if (!calls.length) return showToast('No quota values entered.', 'warning');
+
+    bootstrap.Modal.getInstance(document.getElementById('quotaModal')).hide();
+
+    const results = await Promise.all(calls.map(body =>
+        apiFetch('/api/quota', { method: 'POST', headers: {'Content-Type': 'application/json'}, body: JSON.stringify(body) })
+    ));
+    const failed = results.filter(r => r && !r.ok).length;
+    if (failed) showToast(`${failed} quota(s) failed to apply.`, 'danger');
+    else showToast(`Quota${calls.length > 1 ? 's' : ''} applied.`);
+
+    loadDashboard();
+}