Remove federation functionality and related tests

- Deleted the `federation.rs` module and its associated functionality for federating thoughts to followers.
- Removed the `well_known.rs` module and its WebFinger discovery functionality.
- Eliminated references to federation in the `thought.rs` router and removed the spawning of background tasks for federating thoughts.
- Deleted tests related to WebFinger and user inbox interactions in `activitypub.rs`.
- Updated `Cargo.toml` to remove the `activitypub_federation` dependency.

thoughts-backend/api/src/routers/thought.rs

@@ -20,7 +20,6 @@ use sea_orm::prelude::Uuid;
 use crate::{
     error::ApiError,
     extractor::{AuthUser, Json, OptionalAuthUser, Valid},
-    federation,
     models::{ApiErrorResponse, ParamsErrorResponse},
 };
 
@@ -77,13 +76,6 @@ async fn thoughts_post(
         .await?
         .ok_or(UserError::NotFound)?; // Should not happen if auth is valid
 
-    // Spawn a background task to handle federation without blocking the response
-    tokio::spawn(federation::federate_thought(
-        state.clone(),
-        thought.clone(),
-        author.clone(),
-    ));
-
     let schema = ThoughtSchema::from_models(&thought, &author);
     Ok((StatusCode::CREATED, Json(schema)))
 }