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>

server/src/config.rs

@@ -246,6 +246,8 @@ pub struct ServerConfig {
     pub budget_warning: f64,
     /// "warn" (default) or "block": refuse new model requests once a budget is used up.
     pub budget_action: String,
+    /// Largest file upload in MB (uploads are sent in chunks, so the reverse proxy limit doesn't apply).
+    pub max_upload_mb: u64,
 }
 
 impl Default for ServerConfig {
@@ -263,6 +265,7 @@ impl Default for ServerConfig {
             monthly_budget: 0.0,
             budget_warning: 0.8,
             budget_action: "warn".into(),
+            max_upload_mb: 500,
         }
     }
 }