Add notifications pages and fix RLS/email issues

- Fix RLS policies: Add WITH CHECK clause to all FOR ALL policies
  (fixes 502 errors on admin settings and other updates)
- Add /notifications page for users to view all notifications
- Add /admin/notifications page for admins to create/manage notifications
- Add notifications link to admin sidebar
- Fix NotificationCenter to use goto() for internal navigation
- Fix email.ts to fall back to environment variables for SMTP
  (allows welcome emails to work when app_settings SMTP not configured)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

deploy/init.sql

@@ -749,6 +749,9 @@ CREATE POLICY "Board can manage events"
   TO authenticated
   USING (
     EXISTS (SELECT 1 FROM public.members WHERE id = auth.uid() AND role IN ('board', 'admin'))
+  )
+  WITH CHECK (
+    EXISTS (SELECT 1 FROM public.members WHERE id = auth.uid() AND role IN ('board', 'admin'))
   );
 
 -- EVENT RSVPs POLICIES
@@ -771,6 +774,9 @@ CREATE POLICY "Board can manage all RSVPs"
   TO authenticated
   USING (
     EXISTS (SELECT 1 FROM public.members WHERE id = auth.uid() AND role IN ('board', 'admin'))
+  )
+  WITH CHECK (
+    EXISTS (SELECT 1 FROM public.members WHERE id = auth.uid() AND role IN ('board', 'admin'))
   );
 
 -- PUBLIC RSVPs POLICIES
@@ -791,6 +797,9 @@ CREATE POLICY "Board can manage public RSVPs"
   TO authenticated
   USING (
     EXISTS (SELECT 1 FROM public.members WHERE id = auth.uid() AND role IN ('board', 'admin'))
+  )
+  WITH CHECK (
+    EXISTS (SELECT 1 FROM public.members WHERE id = auth.uid() AND role IN ('board', 'admin'))
   );
 
 -- DOCUMENTS POLICIES
@@ -821,6 +830,9 @@ CREATE POLICY "Admin can manage all documents"
   TO authenticated
   USING (
     EXISTS (SELECT 1 FROM public.members WHERE id = auth.uid() AND role = 'admin')
+  )
+  WITH CHECK (
+    EXISTS (SELECT 1 FROM public.members WHERE id = auth.uid() AND role = 'admin')
   );
 
 -- APP SETTINGS POLICIES
@@ -840,6 +852,9 @@ CREATE POLICY "Admin can manage settings"
   TO authenticated
   USING (
     EXISTS (SELECT 1 FROM public.members WHERE id = auth.uid() AND role = 'admin')
+  )
+  WITH CHECK (
+    EXISTS (SELECT 1 FROM public.members WHERE id = auth.uid() AND role = 'admin')
   );
 
 -- EMAIL TEMPLATES POLICIES
@@ -848,6 +863,9 @@ CREATE POLICY "Admin can manage email templates"
   TO authenticated
   USING (
     EXISTS (SELECT 1 FROM public.members WHERE id = auth.uid() AND role = 'admin')
+  )
+  WITH CHECK (
+    EXISTS (SELECT 1 FROM public.members WHERE id = auth.uid() AND role = 'admin')
   );
 
 -- EMAIL LOGS POLICIES
@@ -864,6 +882,9 @@ CREATE POLICY "Admin can manage email logs"
   TO authenticated
   USING (
     EXISTS (SELECT 1 FROM public.members WHERE id = auth.uid() AND role = 'admin')
+  )
+  WITH CHECK (
+    EXISTS (SELECT 1 FROM public.members WHERE id = auth.uid() AND role = 'admin')
   );
 
 -- INDEXES
@@ -1456,6 +1477,9 @@ CREATE POLICY "Admin can manage all notifications"
   TO authenticated
   USING (
     EXISTS (SELECT 1 FROM public.members WHERE id = auth.uid() AND role = 'admin')
+  )
+  WITH CHECK (
+    EXISTS (SELECT 1 FROM public.members WHERE id = auth.uid() AND role = 'admin')
   );
 
 -- Grant permissions