ui-svelte: add Svelte port of React UI (#487)

Trying out svelte for the UI. The port was done by Claude Code on the iOS app w/ Opus 4.5. 

---

* ui: add Svelte port of React UI

Port the React-based UI to Svelte 5 with the following changes:

- Create new ui-svelte directory with complete Svelte 5 implementation
- Use Svelte stores instead of React contexts for state management
- Implement custom ResizablePanels component to replace react-resizable-panels
- Port all pages: LogViewer, Models, Activity
- Port all components: Header, ConnectionStatus, LogPanel, ModelsPanel, etc.
- Use svelte-spa-router for client-side routing
- Same build output directory (proxy/ui_dist) and base path (/ui/)
- Tailwind CSS 4 with same theme configuration

https://claude.ai/code/session_01F3xXLYsd62gePVSFv7aboP

* ui-svelte: simplify state management

- Remove redundant state syncing pattern in LogPanel and ModelsPanel
- Use store values directly with $ syntax instead of manual subscriptions
- Consolidate duplicate title sync logic in App.svelte
- Use existing syncTitleToDocument() from theme.ts

https://claude.ai/code/session_01F3xXLYsd62gePVSFv7aboP

* ui-svelte: use idiomatic Svelte 5 patterns

- Use $effect for document side effects (theme, title) instead of
  store subscriptions
- Use class: directive for active nav links in Header
- Remove SSR guards (unnecessary for client-only SPA)
- Remove leaked subscription in syncThemeToDocument
- Simplify theme.ts by removing sync functions

https://claude.ai/code/session_01F3xXLYsd62gePVSFv7aboP

* ui-svelte: fix build warnings and improve accessibility

Fix Svelte build warnings and add proper accessibility support
to interactive components.

- add aria-labels to buttons for screen readers
- implement keyboard navigation for resizable separator
- suppress intentional state initialization warnings
- update Makefile to use ui-svelte build directory
- add peer:true to package-lock.json dependencies

* ui-svelte: reorganize navigation and add log view toggle

Make Models the default landing page and add view mode toggle
to the Logs page with persistent state.

- set Models as default route at /
- move Logs to /logs route
- reorder navigation: Models, Activity, Logs
- add view toggle with three modes: Panels, Proxy only, Upstream only
- fix horizontal overflow with width constraints

ui-svelte/src/lib/types.ts

@@ -0,0 +1,42 @@
+export type ConnectionState = "connected" | "connecting" | "disconnected";
+
+export type ModelStatus = "ready" | "starting" | "stopping" | "stopped" | "shutdown" | "unknown";
+
+export interface Model {
+  id: string;
+  state: ModelStatus;
+  name: string;
+  description: string;
+  unlisted: boolean;
+  peerID: string;
+}
+
+export interface Metrics {
+  id: number;
+  timestamp: string;
+  model: string;
+  cache_tokens: number;
+  input_tokens: number;
+  output_tokens: number;
+  prompt_per_second: number;
+  tokens_per_second: number;
+  duration_ms: number;
+}
+
+export interface LogData {
+  source: "upstream" | "proxy";
+  data: string;
+}
+
+export interface APIEventEnvelope {
+  type: "modelStatus" | "logData" | "metrics";
+  data: string;
+}
+
+export interface VersionInfo {
+  build_date: string;
+  commit: string;
+  version: string;
+}
+
+export type ScreenWidth = "xs" | "sm" | "md" | "lg" | "xl" | "2xl";