feat: add pharmacy-product linking system

- Add pharmacy_products table (PostgreSQL + SQLite)
- Add public route GET /api/products/:source/:id/pharmacies
- Add admin CRUD routes for pharmacy-product links
- Add cascade delete when pharmacy is removed
- Update ProductView to show linked pharmacies
- Create PharmacyProductLink admin component
- Add 'Vincular Producto a Farmacia' tab in AdminView

apps/frontend/src/components/admin/AdminComponents.css

@@ -397,6 +397,28 @@
   border-color: var(--border-strong);
 }
 
+/* Source badges */
+.source-badge {
+  display: inline-block;
+  padding: 0.15rem 0.5rem;
+  border-radius: 4px;
+  font-size: 0.75rem;
+  font-weight: 700;
+  text-transform: uppercase;
+  letter-spacing: 0.05em;
+  vertical-align: middle;
+}
+
+.source-badge--cima {
+  background: rgba(37, 99, 235, 0.12);
+  color: #2563eb;
+}
+
+.source-badge--off {
+  background: rgba(16, 185, 129, 0.12);
+  color: #10b981;
+}
+
 /* Pharmacies: search, region import, list filter */
 .pharmacy-tools-card {
   background: var(--surface);