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/queries.rs

@@ -0,0 +1,50 @@
+use uuid::Uuid;
+
+pub struct GetUsersQuery;
+
+#[derive(Debug, Clone, Copy, Default)]
+pub enum ProfileView {
+    History,
+    Trends,
+    Ratings,
+    #[default]
+    Recent,
+}
+
+impl ProfileView {
+    pub fn as_str(&self) -> &'static str {
+        match self {
+            Self::History => "history",
+            Self::Trends => "trends",
+            Self::Ratings => "ratings",
+            Self::Recent => "recent",
+        }
+    }
+}
+
+impl std::str::FromStr for ProfileView {
+    type Err = String;
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        match s {
+            "history" => Ok(Self::History),
+            "trends" => Ok(Self::Trends),
+            "ratings" => Ok(Self::Ratings),
+            "recent" => Ok(Self::Recent),
+            other => Err(format!("unknown profile view: {other}")),
+        }
+    }
+}
+
+pub struct GetUserProfileQuery {
+    pub user_id: Uuid,
+    pub view: ProfileView,
+    pub limit: Option<u32>,
+    pub offset: Option<u32>,
+    pub sort_by: domain::ports::FeedSortBy,
+    pub search: Option<String>,
+    pub is_own_profile: bool,
+}
+
+pub struct GetCurrentProfileQuery {
+    pub user_id: Uuid,
+}