feat: store-level "Group bursts" toggle + idle-window field

Adds group_burst (0/1) + burst_window_sec to the Store type and the
StoreModal editor. Drives finbot's Amazon burst-grouping: when ON, finbot
collapses rapid same-merchant charge bursts into one Firefly transaction
group; the optional idle window (blank = 180s) closes the group.

Backend INSERT/UPDATE carry the fields; GET is SELECT * so reads are free.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/components/StoreModal.tsx

@@ -23,6 +23,8 @@ export function StoreModal({ store, categories, availableTags, onSave, onClose }
     tagList: parseTags(store?.tags ?? ''),
     route: (store?.route ?? 'auto') as Route,
     display_order: store?.display_order ?? 0,
+    group_burst: store?.group_burst ?? 0,
+    burst_window_sec: store?.burst_window_sec ?? null,
   })
 
   // Keep category default once categories load
@@ -137,6 +139,41 @@ export function StoreModal({ store, categories, availableTags, onSave, onClose }
             />
           </div>
 
+          {/* Burst grouping */}
+          <div className="space-y-1.5">
+            <label className="text-xs font-medium text-slate-400 uppercase tracking-wider">
+              Burst Grouping
+            </label>
+            <button
+              type="button"
+              onClick={() => set('group_burst', form.group_burst ? 0 : 1)}
+              className={`w-full flex items-center justify-between rounded-xl px-3.5 py-2.5 text-sm border transition-colors ${
+                form.group_burst
+                  ? 'bg-blue-500/15 border-blue-500/50 text-slate-100'
+                  : 'bg-surface-800 border-white/8 text-slate-400 hover:text-slate-300'
+              }`}
+            >
+              <span>Group rapid same-merchant charges</span>
+              <span className={`text-xs font-semibold ${form.group_burst ? 'text-blue-400' : 'text-slate-500'}`}>
+                {form.group_burst ? 'ON' : 'OFF'}
+              </span>
+            </button>
+            {form.group_burst ? (
+              <div className="flex items-center gap-2 pt-1">
+                <label className="text-xs text-slate-500 whitespace-nowrap">Idle window (sec)</label>
+                <input
+                  type="number"
+                  min={10}
+                  value={form.burst_window_sec ?? ''}
+                  onChange={e => set('burst_window_sec', e.target.value === '' ? null : Number(e.target.value))}
+                  placeholder="180"
+                  className="w-24 bg-surface-800 border border-white/8 rounded-lg px-2.5 py-1.5 text-sm text-slate-200 placeholder:text-slate-600 focus:outline-none focus:border-blue-500/60"
+                />
+                <span className="text-xs text-slate-600">blank = 180s</span>
+              </div>
+            ) : null}
+          </div>
+
           {/* Actions */}
           <div className="flex gap-2 pt-1">
             <button

src/types.ts

@@ -7,6 +7,11 @@ export interface Store {
   tags: string
   route: Route
   display_order: number
+  // Burst-grouping: when 1, finbot collapses same-merchant charge bursts
+  // (e.g. Amazon Subscribe & Save) into one Firefly transaction group.
+  // burst_window_sec = idle gap that closes the group (NULL = global 180s).
+  group_burst: number
+  burst_window_sec: number | null
   created_at: string
 }