Add lead time to recurring templates — generate before actually due

task_templates.lead_days (default 0): scheduler now spawns the task
when (next_due - lead_days) <= today instead of next_due <= today, but
due_date on the created task is still the real next_due — so overdue
and priority handling are unaffected, the task just becomes visible
earlier for prep/booking. Small jobs (AC filter clean) can stay at 0;
bigger ones needing advance notice (septic tank empty-out, contractor
booking) can set 2-3 days or 30 days as needed.

- db.js: lead_days INT NOT NULL DEFAULT 0 (inline for fresh installs,
  ALTER for existing).
- scheduler.js: WHERE (next_due - lead_days) <= $1 — next_due itself
  and the fixed/floating rollover logic are untouched by this.
- templates.js: accept + validate lead_days (>= 0) on create/update.
- Recurring.tsx: lead time field in the template form with contextual
  hint text, plus a small 'generates Nd early' note on list rows that
  have one set.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

frontend/src/pages/Recurring.tsx

@@ -21,6 +21,7 @@ interface TemplateForm {
   interval_value: number
   interval_unit: 'days' | 'weeks' | 'months'
   next_due: string
+  lead_days: number
   template_notes: string
   active: boolean
   schedule_mode: ScheduleMode
@@ -33,7 +34,7 @@ interface TemplateForm {
 
 const EMPTY: TemplateForm = {
   title: '', description: '', location_id: '', asset_id: '', priority: 'medium', unusable: false,
-  interval_value: 1, interval_unit: 'months', next_due: '', template_notes: '', active: true,
+  interval_value: 1, interval_unit: 'months', next_due: '', lead_days: 0, template_notes: '', active: true,
   schedule_mode: 'fixed', group_name: '',
   assignment: { assigned_type: 'staff', assigned_to: null, assigned_to_name: null, contractor_id: null },
   multiLocation: false, location_ids: [],
@@ -105,7 +106,7 @@ export default function Recurring() {
       id: t.id, title: t.title, description: t.description || '',
       location_id: t.location_id, asset_id: t.asset_id || '', priority: t.priority,
       unusable: t.unusable, interval_value: t.interval_value, interval_unit: t.interval_unit,
-      next_due: t.next_due.slice(0, 10), template_notes: t.template_notes, active: t.active,
+      next_due: t.next_due.slice(0, 10), lead_days: t.lead_days, template_notes: t.template_notes, active: t.active,
       schedule_mode: t.schedule_mode, group_name: t.group_name || '',
       assignment: {
         assigned_type: t.assigned_type, assigned_to: t.assigned_to,
@@ -124,7 +125,7 @@ export default function Recurring() {
       title: t.title, description: t.description || '',
       location_id: '', asset_id: '', priority: t.priority,
       unusable: t.unusable, interval_value: t.interval_value, interval_unit: t.interval_unit,
-      next_due: t.next_due.slice(0, 10), template_notes: t.template_notes, active: true,
+      next_due: t.next_due.slice(0, 10), lead_days: t.lead_days, template_notes: t.template_notes, active: true,
       schedule_mode: t.schedule_mode, group_name: t.group_name || '',
       assignment: {
         assigned_type: t.assigned_type, assigned_to: t.assigned_to,
@@ -166,6 +167,7 @@ export default function Recurring() {
         interval_value: form.interval_value,
         interval_unit: form.interval_unit,
         next_due: form.next_due,
+        lead_days: form.lead_days,
         template_notes: form.template_notes,
         active: form.active,
         schedule_mode: form.schedule_mode,
@@ -218,6 +220,7 @@ export default function Recurring() {
           {t.schedule_mode === 'floating' && t.pending_task_id
             ? <span className="badge badge-outline">awaiting completion</span>
             : formatDate(t.next_due)}
+          {t.lead_days > 0 && <span className="field-hint" style={{ display: 'block' }}>generates {t.lead_days}d early</span>}
         </td>
         <td>{t.assigned_type === 'contractor' ? (t.contractor_name || '—') : (t.assigned_to_name || 'Unassigned')}</td>
         <td>{!t.active && <span className="badge badge-outline">paused</span>}</td>
@@ -396,6 +399,15 @@ export default function Recurring() {
               </div>
             </div>
 
+            <div className="field"><label>Lead time (days before due to generate)</label>
+              <input type="number" min={0} value={form.lead_days} onChange={e => setForm({ ...form, lead_days: parseInt(e.target.value) || 0 })} style={{ maxWidth: 120 }} />
+              <div className="field-hint">
+                {form.lead_days > 0
+                  ? `Task appears ${form.lead_days} day${form.lead_days === 1 ? '' : 's'} before it's actually due — due date stays the real one, this just gives warning to prepare or book a contractor.`
+                  : 'Leave at 0 for tasks that don’t need advance warning (e.g. clean AC filter). Larger jobs like a septic tank empty-out might want 30 days so you see it coming.'}
+              </div>
+            </div>
+
             <AssigneeSelect value={form.assignment} onChange={a => setForm({ ...form, assignment: a })} />
 
             <div className="field">