feat: add scramble flag for development text scrambling

This commit introduces a new scramble option to help reduce distractions
during development by scrambling text using rot13. When enabled via the
new `--scramble` flag, text displayed in various views is transformed,
making it easier to focus on layout and behavior without reading the
actual content.

App & Args Updates

  - Added a `scramble: bool` field to the main application state (in `app.rs`).

  - Extended argument parsing (in `args.rs`) to recognize the `--scramble` flag.

NoteOptions Enhancement

  - Introduced a new bit flag `scramble_text` in `NoteOptions` with
    corresponding setter/getter methods.

UI Adjustments

  - Propagated the scramble flag through note rendering functions across
    navigation, timeline, and note view modules.

  - Updated several UI components (e.g., in `nav.rs`, `route.rs`, and
    `contents.rs`) to accept and apply the new note options.

Rot13 Implementation

  - Implemented a helper function (`rot13`) to scramble text
    conditionally when the scramble option is enabled.

This feature is intended for development builds only, offering a way to
obscure text content during UI tweaks and testing.

Signed-off-by: William Casarin <jb55@jb55.com>

crates/notedeck_columns/src/ui/thread.rs

@@ -17,7 +17,7 @@ pub struct ThreadView<'a> {
     unknown_ids: &'a mut UnknownIds,
     img_cache: &'a mut ImageCache,
     selected_note_id: &'a [u8; 32],
-    textmode: bool,
+    note_options: NoteOptions,
     id_source: egui::Id,
     is_muted: &'a MuteFun,
 }
@@ -31,7 +31,7 @@ impl<'a> ThreadView<'a> {
         unknown_ids: &'a mut UnknownIds,
         img_cache: &'a mut ImageCache,
         selected_note_id: &'a [u8; 32],
-        textmode: bool,
+        note_options: NoteOptions,
         is_muted: &'a MuteFun,
     ) -> Self {
         let id_source = egui::Id::new("threadscroll_threadview");
@@ -42,7 +42,7 @@ impl<'a> ThreadView<'a> {
             unknown_ids,
             img_cache,
             selected_note_id,
-            textmode,
+            note_options,
             id_source,
             is_muted,
         }
@@ -101,15 +101,10 @@ impl<'a> ThreadView<'a> {
                     error!("error polling notes into thread timeline: {err}");
                 }
 
-                // This is threadview. We are not the universe view...
-                let is_universe = false;
-                let mut note_options = NoteOptions::new(is_universe);
-                note_options.set_textmode(self.textmode);
-
                 TimelineTabView::new(
                     thread_timeline.current_view(),
                     true,
-                    note_options,
+                    self.note_options,
                     &txn,
                     self.ndb,
                     self.note_cache,