Remove automatic relay configuration and fix channel creation issues

This commit fixes three user-reported issues:

1. **Remove automatic relay configuration**
   - Changed RelayConfig::default() to use new() instead of default_relays()
   - This ensures no relays are added automatically on startup
   - Users must now configure relays manually at startup

2. **Fix channel dialog focus constantly switching**
   - Added focus_requested flag to ChannelDialog
   - request_focus() is now only called once when dialog is first opened
   - Previously it was called every frame, causing constant focus switching
   - This prevented users from typing in the hashtags field

3. **Fix channel creation crash without hashtags**
   - Modified TimelineKind::Hashtag filter creation to handle empty hashtags
   - When no valid hashtags are provided, shows all notes (kind 1) instead of empty filter
   - Previously, empty hashtag vector caused crash due to empty filter set
   - Channels without hashtags now work as a "general" feed showing all notes

All fixes tested and build succeeds without errors.

crates/notedeck_columns/src/relay_config.rs

@@ -64,7 +64,7 @@ impl RelayConfig {
 
 impl Default for RelayConfig {
     fn default() -> Self {
-        Self::default_relays()
+        Self::new()
     }
 }
 

crates/notedeck_columns/src/timeline/kind.rs

@@ -515,7 +515,7 @@ impl TimelineKind {
             }
 
             TimelineKind::Hashtag(hashtag) => {
-                let filters = hashtag
+                let mut filters: Vec<Filter> = hashtag
                     .iter()
                     .filter(|tag| !tag.is_empty())
                     .map(|tag| {
@@ -525,7 +525,17 @@ impl TimelineKind {
                             .tags([tag.to_lowercase().as_str()], 't')
                             .build()
                     })
-                    .collect::<Vec<_>>();
+                    .collect();
+
+                // If no valid hashtags were provided, show all notes
+                if filters.is_empty() {
+                    filters.push(
+                        Filter::new()
+                            .kinds([1])
+                            .limit(filter::default_limit())
+                            .build()
+                    );
+                }
 
                 FilterState::ready(filters)
             }

crates/notedeck_columns/src/ui/channel_dialog.rs

@@ -6,6 +6,7 @@ pub struct ChannelDialog {
     pub name: String,
     pub hashtags: String,
     pub is_open: bool,
+    pub focus_requested: bool,
 }
 
 pub enum ChannelDialogAction {
@@ -19,6 +20,7 @@ impl ChannelDialog {
             name: String::new(),
             hashtags: String::new(),
             is_open: false,
+            focus_requested: false,
         }
     }
 
@@ -26,6 +28,7 @@ impl ChannelDialog {
         self.is_open = true;
         self.name.clear();
         self.hashtags.clear();
+        self.focus_requested = false;
     }
 
     pub fn close(&mut self) {
@@ -70,8 +73,11 @@ impl ChannelDialog {
                             .desired_width(f32::INFINITY),
                     );
 
-                    // Auto-focus on name field when opened
+                    // Auto-focus on name field when first opened
+                    if !self.focus_requested {
                         name_response.request_focus();
+                        self.focus_requested = true;
+                    }
 
                     ui.add_space(16.0);