feat(market): saved searches with in-app alerts (Wallapop-style)

Save the current market search (query + facets) and get notified when a
matching offer appears in your zone while the app is open, with a catch-up
scan on start. Adds a save affordance in the search bar, a saved-searches
list (apply/delete) with a per-search new-match badge, an AppBar entry
badged with the unseen total, and notification-tap routing to the list.
Alerts evaluate against the user's current area, dedup via seen keys, and
skip own/blocked/hidden/non-active offers. en+es strings.

apps/app_seeds/lib/i18n/en.i18n.json

@@ -12,6 +12,19 @@
   "remove": "Remove from favorites",
   "unavailable": "No longer available"
  },
+ "savedSearches": {
+  "title": "Saved searches",
+  "empty": "No saved searches yet. Save a search from the market and we'll tell you when something like it appears in your zone.",
+  "save": "Save this search",
+  "nameLabel": "Name this search",
+  "namePlaceholder": "e.g. Tomatoes near me",
+  "saved": "Search saved — we'll alert you about new matches nearby",
+  "openTooltip": "Saved searches",
+  "delete": "Delete",
+  "deleteConfirm": "Delete this saved search?",
+  "newMatchesBadge": "{n} new",
+  "alert": "New seeds near you: {label}"
+ },
  "seedSaving": {
   "title": "Saving its seed",
   "subtitle": "What it takes to keep the variety true",

apps/app_seeds/lib/i18n/es.i18n.json

@@ -12,6 +12,19 @@
   "remove": "Quitar de favoritos",
   "unavailable": "Ya no está disponible"
  },
+ "savedSearches": {
+  "title": "Búsquedas guardadas",
+  "empty": "Aún no tienes búsquedas guardadas. Guarda una búsqueda desde el mercado y te avisaremos cuando aparezca algo así en tu zona.",
+  "save": "Guardar esta búsqueda",
+  "nameLabel": "Nombra esta búsqueda",
+  "namePlaceholder": "p. ej. Tomates cerca",
+  "saved": "Búsqueda guardada — te avisaremos de lo nuevo que encaje cerca",
+  "openTooltip": "Búsquedas guardadas",
+  "delete": "Eliminar",
+  "deleteConfirm": "¿Eliminar esta búsqueda guardada?",
+  "newMatchesBadge": "{n} nuevas",
+  "alert": "Semillas nuevas cerca: {label}"
+ },
  "seedSaving": {
   "title": "Conservar su semilla",
   "subtitle": "Lo que hace falta para mantener la variedad fiel",