switch to supavisor (however, has bugs)

- when running a query, I get:
```
...webapp::router: search failed: error returned from database: prepared statement "sqlx_s_2" does not exist
```
- this looks similar to this issue: supabase/supavisor#239 (just opened a couple of weeks ago)

backend/shared/src/queryable.rs

@@ -40,6 +40,7 @@ const BASE_URL_STRING: &str = "https://fosdem.org/2024/schedule/event/";
 
 const MAX_POOL_CONNECTIONS: u32 = 10;
 const MAX_RELATED_EVENTS: u8 = 5;
+const DB_REGION: &str = "eu-central-1";
 
 impl Queryable {
     pub async fn connect(
@@ -52,8 +53,8 @@ impl Queryable {
 
         debug!("Connecting to DB");
         let db_url = format!(
-            "postgres://postgres:{}@db.{}.supabase.co/postgres",
-            db_password, db_id
+            "postgres://postgres.{}:{}@aws-0-{}.pooler.supabase.com:6543/postgres",
+            db_id, db_password, DB_REGION
         );
         let pool = PgPoolOptions::new()
             .max_connections(MAX_POOL_CONNECTIONS)

backend/webapp/src/router.rs

@@ -15,7 +15,7 @@ use tower_http::{
     cors::{Any, CorsLayer},
     services::ServeDir,
 };
-use tracing::info;
+use tracing::{error, info};
 use validator::Validate;
 
 use crate::related::related;
@@ -80,7 +80,10 @@ async fn search(
             let html = page.render().unwrap();
             Ok(Html(html))
         }
-        Err(_) => Err("search failed".into()),
+        Err(e) => {
+            error!("search failed: {}", e);
+            Err("search failed".into())
+        }
     }
 }