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/docs/guide/deployment.md

@@ -110,9 +110,16 @@ Set `client_max_body_size` to match your `MAX_UPLOAD_SIZE_MB` value.
 
 ## CI/CD
 
-The GitHub repository has two workflows:
+The GitHub repository has three workflows:
 
-- **release.yml** -- On release, builds a multi-arch Docker image (amd64 + arm64), and pushes to Docker Hub (`stirlingimage/stirling-image`) and GitHub Container Registry (`ghcr.io/stirling-image/stirling-image`).
-- **deploy-docs.yml** -- Builds this documentation site and deploys it to GitHub Pages.
+- **ci.yml** -- Runs automatically on every push and PR. Lints, typechecks, tests, builds, and validates the Docker image (without pushing).
+- **release.yml** -- Triggered manually via `workflow_dispatch`. Runs semantic-release to create a version tag and GitHub release, then builds a multi-arch Docker image (amd64 + arm64) and pushes to Docker Hub (`stirlingimage/stirling-image`) and GitHub Container Registry (`ghcr.io/stirling-image/stirling-image`).
+- **deploy-docs.yml** -- Builds this documentation site and deploys it to GitHub Pages on push to `main`.
 
-Both run automatically. No manual steps needed after merging to `main`.
+To create a release, go to **Actions > Release > Run workflow** in the GitHub UI, or run:
+
+```bash
+gh workflow run release.yml
+```
+
+Semantic-release determines the version from commit history. The `latest` Docker tag always points to the most recent release.

apps/docs/guide/developer.md

@@ -198,12 +198,6 @@ Build the full production image locally:
 docker build -f docker/Dockerfile -t stirling-image:latest .
 ```
 
-Build the lite image (no Python/AI, ~1.5 GB):
-
-```bash
-docker build --build-arg VARIANT=lite -f docker/Dockerfile -t stirling-image:lite .
-```
-
 Use BuildKit cache mounts for faster rebuilds:
 
 ```bash

apps/docs/guide/docker-tags.md

@@ -118,9 +118,6 @@ volumes:
 
 ## Migration from previous tags
 
-If you were using `:lite` or `:cuda` tags, switch to `:latest`:
-
-- **From `:lite`**: Pull `:latest`. You now have all AI tools included.
-- **From `:cuda`**: Pull `:latest` and keep `--gpus all`. Same GPU support, unified image.
+If you were using the `:cuda` tag, switch to `:latest` and keep `--gpus all`. Same GPU support, unified image.
 
 Your data and settings are preserved in the volumes.

apps/docs/guide/getting-started.md

@@ -14,21 +14,11 @@ docker run -d \
 
 Open `http://localhost:1349` in your browser. Log in with `admin` / `admin`.
 
-::: tip Lite image
-Don't need AI tools (background removal, upscaling, OCR, face blur, object eraser)? Use the lite image instead - 1.5 GB vs 11 GB:
-
-```bash
-stirlingimage/stirling-image:lite
-```
-
-All 27+ image processing tools work the same. See [Docker Tags](./docker-tags) for the full comparison.
-:::
-
 ::: tip GPU acceleration
-Have an NVIDIA GPU? The CUDA image auto-detects your GPU and accelerates background removal (2.7x), upscaling (3x), and OCR (1.5x):
+Have an NVIDIA GPU? Add `--gpus all` to accelerate background removal (2.7x), upscaling (3x), and OCR (1.5x):
 
 ```bash
-docker run -d --gpus all -p 1349:1349 -v stirling-data:/data stirlingimage/stirling-image:cuda
+docker run -d --gpus all -p 1349:1349 -v stirling-data:/data stirlingimage/stirling-image:latest
 ```
 
 Requires [NVIDIA Container Toolkit](https://docs.nvidia.com/datacenter/cloud-native/container-toolkit/latest/install-guide.html). Falls back to CPU if no GPU is found. See [Docker Tags](./docker-tags) for details and benchmarks.