Add Web Push, guided start screen, SVG icons, chunked uploads, rename

- Web Push (VAPID + RFC 8291, pure Rust): permission/question/finished
  notifications while no app window is visible; settings with test button
- Guided new-session flow: task, craft target (website/app/game/old
  software/fresh), clean room or deep, description, model, folder
  (new, existing or cloned git repository); originals upload to original/
- Craft phase bar (craft_phase tool) for study/specify/build/check/ready
- Chunked uploads (8 MB) up to server.max_upload_mb (default 500 MB)
- All UI glyphs and emojis replaced by themeable SVG icons
- Rename dialog with manual name or model-generated suggestion

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

web/src/components/Markdown.tsx

@@ -1,3 +1,4 @@
+import { Icon } from "./Icon";
 import { memo, useState, type ReactNode } from "react";
 import ReactMarkdown from "react-markdown";
 import remarkGfm from "remark-gfm";
@@ -36,7 +37,7 @@ export function SvgBlock({ code, children }: { code: string; children?: ReactNod
         <img src={url} alt="SVG" />
       </FileFigure>
       <button className="small ghost" onClick={() => setShowCode(!showCode)}>
-        {showCode ? "▾ SVG" : "▸ SVG"}
+        <Icon name={showCode ? "chevron-down" : "chevron-right"} /> SVG
       </button>
       {showCode && children}
     </div>