Add terminal client, memory, model fallback, version and install improvements

- codecraft: full-screen terminal client (ratatui) – local tools and files,
  models via the CodeCraft server gateway or own providers (standalone with a
  guided setup), slash commands, @files, permission dialogs, resume, update
- Static Linux CLI builds (x86_64/aarch64, cargo-zigbuild) served by the
  server: /cli/install.sh and /cli/download/<target>
- Project memory (remember tool, .codecraft/memory.md) and personal memory
- Model fallback when a host is unreachable or a budget is used up
- Version/commit in UI and health, daily release check, "What's new" dialog
- PWA: install button, maskable icon, manifest id and screenshots
- Case-insensitive detection of connection errors for retries

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

server/src/config.rs

@@ -254,6 +254,8 @@ pub struct ServerConfig {
     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,
+    /// Where to look for new releases (Gitea/GitHub "latest release" API); empty = no check.
+    pub update_url: String,
 }
 
 impl Default for ServerConfig {
@@ -272,6 +274,7 @@ impl Default for ServerConfig {
             budget_warning: 0.8,
             budget_action: "warn".into(),
             max_upload_mb: 500,
+            update_url: "https://git.familie-zink.org/api/v1/repos/zink/codecraft/releases/latest".into(),
         }
     }
 }