feat: server-authoritative case window via users.toml

The /api/oneliners time window is now read per-user from users.toml
(window_hours, default 72h). Clients no longer carry a window:
client.toml oneliner_window_hours, SyncConfig.window_hours, the
?hours=N query param, and the render_case_list cutoff filter are
gone. ETag suffix keeps the effective hours so an admin edit to
users.toml invalidates client caches on the next request.
OnelinersResponse.window_hours stays in the wire format, but now
exists solely to anchor client reconciliation.

doctate-common/src/oneliners.rs

@@ -48,7 +48,13 @@ pub enum OnelinerState {
 pub struct OnelinersResponse {
     /// RFC3339 UTC timestamp at which the server built this response.
     pub as_of: String,
-    /// Effective window (after server-side clamp).
+    /// Server-authoritative window the response covers, in hours.
+    /// Derived from the user's `window_hours` entry in `users.toml`.
+    /// **Clients must not use this value to apply a display filter** —
+    /// the oneliners list is already exactly what the server wants shown.
+    /// The field exists solely so reconciliation logic can anchor its
+    /// "outside the window" rule (see
+    /// `doctate-client-core::CaseStore::reconcile_with_server_snapshot`).
     pub window_hours: u32,
     /// Oneliners of cases whose earliest recording sits inside the window,
     /// sorted newest-first by `created_at`.