refactor: group use cases into DDD bounded contexts

Flat use_cases/ (44 files) + monolithic commands.rs/queries.rs
split into diary/, movies/, watchlist/, import/, auth/, users/,
integrations/, search/, person/, federation/ — each with own
commands.rs, queries.rs, and use case modules.

Inline tests extracted to sibling tests/ dirs.

crates/application/src/users/get_current_profile.rs

@@ -0,0 +1,32 @@
+use domain::errors::DomainError;
+
+use crate::{context::AppContext, users::queries::GetCurrentProfileQuery};
+
+pub struct CurrentProfileData {
+    pub username: String,
+    pub bio: Option<String>,
+    pub avatar_url: Option<String>,
+}
+
+pub async fn execute(
+    ctx: &AppContext,
+    query: GetCurrentProfileQuery,
+) -> Result<CurrentProfileData, DomainError> {
+    let user_id = domain::value_objects::UserId::from_uuid(query.user_id);
+    let user = ctx
+        .repos
+        .user
+        .find_by_id(&user_id)
+        .await?
+        .ok_or_else(|| DomainError::NotFound("User not found".into()))?;
+
+    let avatar_url = user
+        .avatar_path()
+        .map(|path| format!("{}/images/{}", ctx.config.base_url, path));
+
+    Ok(CurrentProfileData {
+        username: user.username().value().to_string(),
+        bio: user.bio().map(|s| s.to_string()),
+        avatar_url,
+    })
+}