feat(electrobun): wire persistence — SQLite, 17 themes, font system

Persistence:
- bun:sqlite at ~/.config/agor/settings.db (WAL mode, 500ms busy_timeout)
- 4 tables: schema_version, settings, projects, custom_themes
- 5 RPC handlers: settings.get/set/getAll, projects get/set

Theme system (LIVE switching):
- All 17 themes ported from Tauri (4 Catppuccin + 7 Editor + 6 Deep Dark)
- applyCssVars() sets 26 --ctp-* vars on document.documentElement
- Parallel xterm ITheme mapping per theme
- theme-store.svelte.ts: Svelte 5 rune store, persists to SQLite

Font system:
- font-store.svelte.ts: UI/terminal font family + size
- Live CSS var application (--ui-font-family/size, --term-font-family/size)
- onTermFontChange() callback registry for terminal instances
- Persists all 4 font settings to SQLite

AppearanceSettings wired: 17-theme grouped dropdown, font steppers
Init on startup: restores saved theme + fonts from SQLite

ui-electrobun/src/mainview/App.svelte

@@ -1,8 +1,12 @@
 <script lang="ts">
+  import { onMount } from 'svelte';
   import ProjectCard from './ProjectCard.svelte';
   import SettingsDrawer from './SettingsDrawer.svelte';
   import CommandPalette from './CommandPalette.svelte';
   import ToastContainer from './ToastContainer.svelte';
+  import { themeStore } from './theme-store.svelte.ts';
+  import { fontStore } from './font-store.svelte.ts';
+  import { appRpc } from './main.ts';
 
   // ── Types ─────────────────────────────────────────────────────
   type AgentStatus = 'running' | 'idle' | 'stalled';
@@ -78,6 +82,12 @@
     },
   ];
 
+  // ── Init theme + fonts on mount ────────────────────────────────
+  onMount(() => {
+    themeStore.initTheme(appRpc).catch(console.error);
+    fontStore.initFonts(appRpc).catch(console.error);
+  });
+
   // ── Reactive state ─────────────────────────────────────────────
   let settingsOpen    = $state(false);
   let paletteOpen     = $state(false);