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

.github/workflows/deploy-docs.yml

@@ -35,7 +35,7 @@ jobs:
       - name: Install dependencies
         run: pnpm install --frozen-lockfile
       - name: Build Docs
-        run: pnpm --filter @stirling-image/docs docs:build
+        run: pnpm --filter @ashim/docs docs:build
       - name: Upload artifact
         uses: actions/upload-pages-artifact@v3
         with: