feat: add tag deletion endpoint with CLI support

.sqlx/query-dd0d0e3fd03f130aab947d13580796eee9a786e2ca01d339fd0e8356f8ad3824.json

@@ -0,0 +1,14 @@
+{
+  "db_name": "PostgreSQL",
+  "query": "DELETE FROM tags WHERE id = $1",
+  "describe": {
+    "columns": [],
+    "parameters": {
+      "Left": [
+        "Uuid"
+      ]
+    },
+    "nullable": []
+  },
+  "hash": "dd0d0e3fd03f130aab947d13580796eee9a786e2ca01d339fd0e8356f8ad3824"
+}

src/cli/api/tags.rs

@@ -35,6 +35,7 @@ pub async fn run(
             icon,
             color,
         } => update(client, &slug, name, new_slug, icon, color, json).await,
+        TagsCommand::Delete { reference } => delete(client, &reference, json).await,
     }
 }
 
@@ -171,3 +172,24 @@ async fn update(
 
     Ok(())
 }
+
+/// Delete a tag
+async fn delete(
+    client: ApiClient,
+    reference: &str,
+    json: bool,
+) -> Result<(), Box<dyn std::error::Error>> {
+    let response = client
+        .delete_auth(&format!("/api/tags/{}", reference))
+        .await?;
+    let response = check_response(response).await?;
+    let deleted: ApiTag = response.json().await?;
+
+    if json {
+        println!("{}", serde_json::to_string_pretty(&deleted)?);
+    } else {
+        output::success(&format!("Deleted tag: {}", deleted.name));
+    }
+
+    Ok(())
+}

src/cli/mod.rs

@@ -229,6 +229,13 @@ pub enum TagsCommand {
         #[arg(long)]
         color: Option<String>,
     },
+
+    /// Delete a tag
+    Delete {
+        /// Tag slug or UUID
+        #[arg(name = "ref")]
+        reference: String,
+    },
 }
 
 #[derive(Subcommand, Debug)]

src/db/tags.rs

@@ -120,6 +120,13 @@ pub async fn get_tag_by_ref(pool: &PgPool, ref_str: &str) -> Result<Option<DbTag
     }
 }
 
+pub async fn delete_tag(pool: &PgPool, id: Uuid) -> Result<(), sqlx::Error> {
+    sqlx::query!("DELETE FROM tags WHERE id = $1", id)
+        .execute(pool)
+        .await?;
+    Ok(())
+}
+
 pub async fn get_all_tags_with_counts(pool: &PgPool) -> Result<Vec<(DbTag, i32)>, sqlx::Error> {
     let rows = sqlx::query!(
         r#"

src/handlers/tags.rs

@@ -252,6 +252,66 @@ pub async fn update_tag_handler(
     }
 }
 
+/// Delete a tag (requires authentication)
+pub async fn delete_tag_handler(
+    State(state): State<Arc<AppState>>,
+    axum::extract::Path(ref_str): axum::extract::Path<String>,
+    jar: axum_extra::extract::CookieJar,
+) -> impl IntoResponse {
+    if auth::check_session(&state, &jar).is_none() {
+        return auth::require_auth_response().into_response();
+    }
+
+    // Fetch tag before deletion to return it
+    let tag = match db::get_tag_by_ref(&state.pool, &ref_str).await {
+        Ok(Some(tag)) => tag,
+        Ok(None) => {
+            return (
+                StatusCode::NOT_FOUND,
+                Json(serde_json::json!({
+                    "error": "Not found",
+                    "message": "Tag not found"
+                })),
+            )
+                .into_response();
+        }
+        Err(err) => {
+            tracing::error!(error = %err, "Failed to fetch tag before deletion");
+            return (
+                StatusCode::INTERNAL_SERVER_ERROR,
+                Json(serde_json::json!({
+                    "error": "Internal server error",
+                    "message": "Failed to delete tag"
+                })),
+            )
+                .into_response();
+        }
+    };
+
+    // Delete tag (CASCADE handles project_tags and tag_cooccurrence)
+    match db::delete_tag(&state.pool, tag.id).await {
+        Ok(()) => {
+            tracing::info!(tag_id = %tag.id, tag_name = %tag.name, "Tag deleted");
+
+            // Invalidate cached pages - tags appear on project pages
+            state.isr_cache.invalidate("/").await;
+
+            Json(tag.to_api_tag()).into_response()
+        }
+        Err(err) => {
+            tracing::error!(error = %err, "Failed to delete tag");
+            (
+                StatusCode::INTERNAL_SERVER_ERROR,
+                Json(serde_json::json!({
+                    "error": "Internal server error",
+                    "message": "Failed to delete tag"
+                })),
+            )
+                .into_response()
+        }
+    }
+}
+
 /// Get related tags by cooccurrence
 pub async fn get_related_tags_handler(
     State(state): State<Arc<AppState>>,

src/routes.rs

@@ -65,7 +65,9 @@ pub fn api_routes() -> Router<Arc<AppState>> {
         )
         .route(
             "/tags/{ref}",
-            get(handlers::get_tag_handler).put(handlers::update_tag_handler),
+            get(handlers::get_tag_handler)
+                .put(handlers::update_tag_handler)
+                .delete(handlers::delete_tag_handler),
         )
         .route(
             "/tags/{ref}/related",