Add dedicated Companion Planting page

Backend: new GET /api/v1/companions endpoint returning all companion
relationships with joined species names, slugs and images. Adds
CompanionWithNames model and list_all DB query.

Frontend: new /companions route with search bar, beneficial (green)
and antagonistic (red) sections, species thumbnails, mechanism text,
source links, and species detail links. Full DE/EN i18n support.

herbapi-api/src/api/companions.rs

@@ -6,6 +6,13 @@ use crate::db::{companions as db, models::*};
 use crate::error::{AppError, Result};
 use crate::state::AppState;
 
+pub async fn list_all(
+    State(state): State<AppState>,
+) -> Result<Json<Vec<CompanionWithNames>>> {
+    let companions = db::list_all(&state.pool).await?;
+    Ok(Json(companions))
+}
+
 pub async fn list_for_species(
     State(state): State<AppState>,
     Path(r): Path<String>,

herbapi-api/src/api/mod.rs

@@ -1,5 +1,6 @@
 mod companions;
 mod cultivars;
+mod docs;
 mod families;
 mod health;
 mod images;
@@ -35,7 +36,7 @@ pub fn router(state: AppState) -> Router {
         .route("/api/v1/suppliers", get(suppliers::list).post(suppliers::create))
         .route("/api/v1/suppliers/{ref}", get(suppliers::get_by_slug).put(suppliers::update).delete(suppliers::remove))
         // Companions
-        .route("/api/v1/companions", post(companions::create))
+        .route("/api/v1/companions", get(companions::list_all).post(companions::create))
         .route("/api/v1/companions/{id}", delete(companions::remove))
         // Images
         .route("/api/v1/images/{entity_type}/{entity_id}", get(images::list_for_entity))
@@ -45,6 +46,9 @@ pub fn router(state: AppState) -> Router {
         .route("/img/{*path}", get(images::serve_image))
         // Search
         .route("/api/v1/search", get(search::search))
+        // API docs
+        .route("/api/openapi.yaml", get(docs::openapi_yaml))
+        .route("/api/docs", get(docs::swagger_ui))
         // OIDC auth
         .route("/auth/oidc/login", get(crate::auth::oidc::login))
         .route("/auth/oidc/callback", get(crate::auth::oidc::callback))

herbapi-api/src/db/companions.rs

@@ -2,7 +2,29 @@ use sqlx::PgPool;
 use uuid::Uuid;
 
 use crate::error::{AppError, Result};
-use super::models::{CompanionRelationship, CreateCompanion};
+use super::models::{CompanionRelationship, CompanionWithNames, CreateCompanion};
+
+pub async fn list_all(pool: &PgPool) -> Result<Vec<CompanionWithNames>> {
+    sqlx::query_as::<_, CompanionWithNames>(
+        "SELECT cr.id, cr.species_a_id, cr.species_b_id, cr.relationship,
+                cr.mechanism, cr.source_url, cr.created_at,
+                sa.name_scientific AS species_a_scientific,
+                sa.name_de AS species_a_de,
+                sa.slug AS species_a_slug,
+                sa.primary_image_key AS species_a_image,
+                sb.name_scientific AS species_b_scientific,
+                sb.name_de AS species_b_de,
+                sb.slug AS species_b_slug,
+                sb.primary_image_key AS species_b_image
+         FROM companion_relationships cr
+         JOIN species sa ON cr.species_a_id = sa.id
+         JOIN species sb ON cr.species_b_id = sb.id
+         ORDER BY sa.name_scientific, sb.name_scientific"
+    )
+    .fetch_all(pool)
+    .await
+    .map_err(Into::into)
+}
 
 pub async fn list_for_species(pool: &PgPool, species_id: Uuid) -> Result<Vec<CompanionRelationship>> {
     sqlx::query_as::<_, CompanionRelationship>(

herbapi-api/src/db/models.rs

@@ -438,6 +438,25 @@ pub struct CompanionRelationship {
     pub created_at: DateTime<Utc>,
 }
 
+#[derive(Debug, FromRow, Serialize)]
+pub struct CompanionWithNames {
+    pub id: Uuid,
+    pub species_a_id: Uuid,
+    pub species_b_id: Uuid,
+    pub relationship: String,
+    pub mechanism: Option<String>,
+    pub source_url: Option<String>,
+    pub created_at: DateTime<Utc>,
+    pub species_a_scientific: String,
+    pub species_a_de: Option<String>,
+    pub species_a_slug: String,
+    pub species_a_image: Option<String>,
+    pub species_b_scientific: String,
+    pub species_b_de: Option<String>,
+    pub species_b_slug: String,
+    pub species_b_image: Option<String>,
+}
+
 #[derive(Debug, Deserialize)]
 pub struct CreateCompanion {
     pub species_a_id: Uuid,