Frontend overhaul: NetBox-style detail pages, selectable columns, data sources

- Cultivar/species detail pages rewritten with two-column card layout, attribute tables, em-dash placeholders
- Column toggle + per-page selector on all list pages (families, species, cultivars, suppliers)
- Species list: table/card view toggle with family, layer, N-fixer, uses columns
- Cultivar detail: supplier links with SKU/price/product URL, species info section
- Data sources page (/sources) with attribution for all 10 data sources
- Fixed Cultivar/Species structs with #[serde(default)] for API compatibility
- Added table_controls component (reusable column toggle + per-page selector)
- Removed max-width constraint on content area for full-width tables
- Fixed route conflicts: merged {slug}/{id} into single {ref} routes
- Removed PostgreSQL enum types (plant_layer, drought_tolerance, etc.) in favor of TEXT
- Fixed API per_page parameter support across all list endpoints

herbapi-api/migrations/006_create_suppliers.sql

@@ -17,8 +17,8 @@ CREATE TABLE cultivar_suppliers (
     supplier_id     UUID NOT NULL REFERENCES suppliers(id) ON DELETE CASCADE,
     article_number  TEXT,
     product_url     TEXT,
-    price_eur       NUMERIC(8,2),
-    pack_size       NUMERIC(8,2),
+    price_eur       DOUBLE PRECISION,
+    pack_size       DOUBLE PRECISION,
     pack_unit       TEXT,
     last_checked_at TIMESTAMPTZ,
     created_at      TIMESTAMPTZ NOT NULL DEFAULT NOW(),