Sortable item table, Size in its own column, Subscribed as an icon

- Every column heading sorts (kept, title, feed, file type, size,
  published); a second click reverses it. The server sorts through a
  fixed whitelist (order_sql), so it covers the whole list, not the
  fifty loaded; the choice is remembered in the browser.
- Size is its own column and shows KB for small files instead of
  "0 MB". The Item heading is Title.
- Popular/Directory/Add feed: Subscribed is a green circle-check.
- Tests: every sort column runs and orders both ways (db); the table
  sorts by title both ways and remembers across a reload (browser).

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_0173mGu6rK18Ne7UGTwAaVJV

src/web.rs

@@ -824,6 +824,12 @@ struct Page {
     filter: Option<String>,
     #[serde(default)]
     q: Option<String>,
+    /// A column name and asc or desc. Anything unrecognised is newest first: the name picks a
+    /// fixed expression in the query and never reaches it itself.
+    #[serde(default)]
+    sort: Option<String>,
+    #[serde(default)]
+    dir: Option<String>,
 }
 
 fn fifty() -> i64 {
@@ -864,7 +870,12 @@ fn entry_page(
     let filter = crate::db::Filter::parse(page.filter.as_deref().unwrap_or("all"));
     let search = page.q.as_deref().map(str::trim).filter(|q| !q.is_empty());
     let db = &state.ctx.db;
-    let mut rows = db.entries_in(user_id, feed, filter, search, page.offset, page.limit.clamp(1, 200))?;
+    let order = crate::db::order_sql(
+        page.sort.as_deref().unwrap_or("published"),
+        page.dir.as_deref().unwrap_or("desc"),
+    );
+    let mut rows =
+        db.entries_in(user_id, feed, filter, search, page.offset, page.limit.clamp(1, 200), &order)?;
     // Feed HTML is untrusted: it reaches the page only after ammonia has been through it.
     for row in &mut rows {
         if let Some(d) = &row.description {