Add file badges, menu icons, LSP diagnostics, robust compaction

- Files in chat: preview with type/size badges and file name; attachment chips
- Menu and settings tabs with icons
- Heatmap: distinct colour for empty hours, hourly labels
- Context chip shows used/total tokens (e.g. 221k/240k) plus percent
- LSP client: diagnostics appended to edit/write results and a diagnostics tool
  (typescript-language-server, pyright, rust-analyzer, gopls, clangd; sandboxed)
- Compaction summarizes a plain transcript and retries once on empty output
- files/stat endpoint

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

web/src/components/Sidebar.tsx

@@ -91,20 +91,25 @@ export function Sidebar({ open, activeId, section }: { open: boolean; activeId?:
         </span>
         <ThemeModeButton />
         <button className="small ghost" onClick={() => post("/auth/logout").then(() => location.reload())}>
+          <span className="nav-icon" aria-hidden>🚪</span>
           {t("nav.logout")}
         </button>
       </div>
       <div className="sidebar-foot">
         <button className={`ghost ${section === "files" ? "active" : ""}`} onClick={() => navigate("/files")}>
+          <span className="nav-icon" aria-hidden>📁</span>
           {t("nav.files")}
         </button>
         <button className={`ghost ${section === "images" ? "active" : ""}`} onClick={() => navigate("/images")}>
+          <span className="nav-icon" aria-hidden>🖼️</span>
           {t("nav.images")}
         </button>
         <button className={`ghost ${section === "stats" ? "active" : ""}`} onClick={() => navigate("/stats")}>
+          <span className="nav-icon" aria-hidden>📊</span>
           {t("nav.stats")}
         </button>
         <button className={`ghost ${section === "settings" ? "active" : ""}`} onClick={() => navigate("/settings")}>
+          <span className="nav-icon" aria-hidden>🔧</span>
           {t("nav.settings")}
         </button>
       </div>