refactor: remove lite variant, fix release workflow

- Remove all lite/full variant logic from frontend, API, shared constants,
  docs, and tests (single unified Docker image only)
- Replace single QEMU multi-arch Docker build with per-architecture native
  builds (amd64 + arm64) and manifest merge to fix disk space exhaustion
- Add disk cleanup step and per-platform build cache scopes
- Switch release trigger from push to workflow_dispatch
- Add GitHub issue templates and PR template

apps/web/src/stores/settings-store.ts

@@ -2,8 +2,6 @@ import { create } from "zustand";
 import { apiGet } from "@/lib/api";
 
 interface SettingsState {
-  variant: "full" | "lite";
-  variantUnavailableTools: string[];
   disabledTools: string[];
   experimentalEnabled: boolean;
   loaded: boolean;
@@ -11,8 +9,6 @@ interface SettingsState {
 }
 
 export const useSettingsStore = create<SettingsState>((set, get) => ({
-  variant: "full",
-  variantUnavailableTools: [],
   disabledTools: [],
   experimentalEnabled: false,
   loaded: false,
@@ -22,19 +18,15 @@ export const useSettingsStore = create<SettingsState>((set, get) => ({
     try {
       const data = await apiGet<{
         settings: Record<string, string>;
-        variant: "full" | "lite";
-        variantUnavailableTools: string[];
       }>("/v1/settings");
 
       set({
-        variant: data.variant ?? "full",
-        variantUnavailableTools: data.variantUnavailableTools ?? [],
         disabledTools: data.settings.disabledTools ? JSON.parse(data.settings.disabledTools) : [],
         experimentalEnabled: data.settings.enableExperimentalTools === "true",
         loaded: true,
       });
     } catch {
-      // Settings fetch failed - default to full with no disabled tools
+      // Settings fetch failed - default to no disabled tools
       set({ loaded: true });
     }
   },