chore: rename Stirling-Image to ashim across entire codebase

Complete rebrand from Stirling-Image to ashim following the project
move to https://github.com/ashim-hq/ashim.

Changes across 117 files:
- Package scope: @stirling-image/* → @ashim/*
- GitHub URLs: stirling-image/stirling-image → ashim-hq/ashim
- Docker Hub: stirlingimage/stirling-image → ashimhq/ashim
- GitHub Pages: stirling-image.github.io → ashim-hq.github.io
- All branding text: "Stirling Image" → "ashim"
- Docker service/volumes/user: stirling → ashim
- Database: stirling.db → ashim.db
- localStorage keys: stirling-token → ashim-token
- Environment variables: STIRLING_GPU → ASHIM_GPU
- Python cache dirs: .cache/stirling-image → .cache/ashim
- SVG filter IDs, test prefixes, and all other references

apps/web/src/pages/fullscreen-grid-page.tsx

@@ -1,5 +1,5 @@
-import type { CategoryInfo, Tool } from "@stirling-image/shared";
-import { CATEGORIES, TOOLS } from "@stirling-image/shared";
+import type { CategoryInfo, Tool } from "@ashim/shared";
+import { CATEGORIES, TOOLS } from "@ashim/shared";
 import * as icons from "lucide-react";
 import { Eye, EyeOff, FileImage, LayoutGrid, List, Search } from "lucide-react";
 import { useEffect, useMemo, useState } from "react";
@@ -69,7 +69,7 @@ export function FullscreenGridPage() {
             className="flex items-center gap-2 text-lg font-bold text-foreground shrink-0"
           >
             <GemLogo className="h-6 w-6 text-primary" />
-            Stirling <span className="text-primary">Image</span>
+            <span className="text-primary">ashim</span>
           </Link>
 
           {/* Search */}