fix: close all remaining known gaps across modules

Every 'read-only placeholder' and 'missing functionality' gap from the
QA audit is now resolved:

COURSES — categories/instructors/locations can now be deleted:
- Added update/delete methods to course-reference-data.service.ts
- Added deleteCategory/deleteInstructor/deleteLocation server actions
- Created DeleteRefDataButton client component with confirmation dialog
- Wired delete buttons into all three table pages

BOOKINGS — calendar month navigation now works:
- Calendar was hardcoded to current month with disabled prev/next
- Added year/month search params for server-side month rendering
- Replaced disabled buttons with Link-based navigation
- Verified: clicking next/prev correctly renders different months

DOCUMENTS — templates page now reads from database:
- Was hardcoded empty array; now queries document_templates table
- Table exists since migration 20260414000006_shared_templates.sql

FISCHEREI — statistics page shows real data:
- Replaced dashed-border placeholder with 6 real stat cards
- Queries waters, species, stocking, catch_books, leases, permits
- Shows counts + stocking costs + pending catch books
- Falls back to helpful message when no data exists

VERBAND — statistics page shows real KPIs:
- Added server-side data fetching (clubs, members, fees)
- Passes activeClubs, totalMembers, openFees as props
- Added 4 KPI cards: Aktive Vereine, Gesamtmitglieder,
  ∅ Mitglieder/Verein, Offene Beiträge
- Kept existing trend charts below KPI cards

apps/web/app/[locale]/home/[account]/documents/templates/page.tsx

@@ -26,13 +26,19 @@ export default async function DocumentTemplatesPage({ params }: PageProps) {
 
   if (!acct) return <AccountNotFound />;
 
-  // Document templates are stored locally for now — placeholder for future DB integration
-  const templates: Array<{
-    id: string;
-    name: string;
-    type: string;
-    description: string;
-  }> = [];
+  // Fetch document templates from DB
+  const { data: templates } = await client
+    .from('document_templates')
+    .select('id, name, template_type, description')
+    .eq('account_id', acct.id)
+    .order('name');
+
+  const templatesList = (templates ?? []).map((t: any) => ({
+    id: String(t.id),
+    name: String(t.name),
+    type: String(t.template_type ?? '—'),
+    description: String(t.description ?? ''),
+  }));
 
   return (
     <CmsPageShell account={account} title={t('templates.title')}>
@@ -50,7 +56,7 @@ export default async function DocumentTemplatesPage({ params }: PageProps) {
         </div>
 
         {/* Table or Empty State */}
-        {templates.length === 0 ? (
+        {templatesList.length === 0 ? (
           <EmptyState
             icon={<FileText className="h-8 w-8" />}
             title={t('templates.noTemplates')}
@@ -61,7 +67,7 @@ export default async function DocumentTemplatesPage({ params }: PageProps) {
           <Card>
             <CardHeader>
               <CardTitle>
-                {t('templates.allTemplates', { count: templates.length })}
+                {t('templates.allTemplates', { count: templatesList.length })}
               </CardTitle>
             </CardHeader>
             <CardContent>
@@ -81,7 +87,7 @@ export default async function DocumentTemplatesPage({ params }: PageProps) {
                     </tr>
                   </thead>
                   <tbody>
-                    {templates.map((template) => (
+                    {templatesList.map((template) => (
                       <tr
                         key={template.id}
                         className="hover:bg-muted/30 border-b"