feat: image storage generalization, user profile, and federation polish

- Replace PosterStorage with generic ImageStorage port (IMAGE_STORAGE_BACKEND/PATH env vars)
- Rename poster-storage crate to image-storage; serve at /images/{*key}
- Add bio and avatar_path to User model (migration 0009_user_profile)
- update_profile use case with avatar upload, mime validation, old avatar cleanup
- GET/PUT /api/v1/profile and GET/POST /settings/profile HTML page
- Enrich AP Person actor with summary, icon, url, discoverable fields
- Store remote actor avatar_url (migration 0010_ap_remote_actor_avatar)
- Shared inbox delivery via collect_inboxes deduplication
- Broadcast Update(Person) to followers on UserUpdated event
- Paginated outbox: OrderedCollection + OrderedCollectionPage with cursor
- Announce/boost tracking in ap_announces table (migration 0011_ap_announces)

crates/presentation/src/handlers/images.rs

@@ -0,0 +1,25 @@
+use axum::{
+    extract::{Path, State},
+    http::{StatusCode, header},
+    response::IntoResponse,
+};
+
+use crate::state::AppState;
+
+pub async fn get_image(
+    State(state): State<AppState>,
+    Path(key): Path<String>,
+) -> impl IntoResponse {
+    if key.starts_with("http://") || key.starts_with("https://") {
+        return axum::response::Redirect::temporary(&key).into_response();
+    }
+    match state.app_ctx.image_storage.get(&key).await {
+        Ok(bytes) => {
+            let mime = infer::get(&bytes)
+                .map(|t| t.mime_type())
+                .unwrap_or("application/octet-stream");
+            ([(header::CONTENT_TYPE, mime)], bytes).into_response()
+        }
+        Err(_) => StatusCode::NOT_FOUND.into_response(),
+    }
+}