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

.github/ISSUE_TEMPLATE/bug_report.yml

@@ -0,0 +1,85 @@
+name: Bug Report
+description: Something isn't working as expected
+labels: ["bug"]
+body:
+  - type: checkboxes
+    id: checklist
+    attributes:
+      label: Before submitting
+      options:
+        - label: I searched existing issues and didn't find a duplicate
+          required: true
+        - label: I'm running the latest version of Stirling Image
+          required: true
+
+  - type: textarea
+    id: description
+    attributes:
+      label: Description
+      description: What happened, and what did you expect to happen?
+      placeholder: |
+        When I try to resize an image, the output is blank.
+        I expected the resized image to be returned normally.
+    validations:
+      required: true
+
+  - type: textarea
+    id: steps
+    attributes:
+      label: Steps to reproduce
+      description: How can we reproduce this?
+      placeholder: |
+        1. Upload a PNG image
+        2. Select "Resize" tool
+        3. Set width to 500
+        4. Click "Process"
+        5. Downloaded file is 0 bytes
+    validations:
+      required: true
+
+  - type: textarea
+    id: docker-setup
+    attributes:
+      label: Docker setup
+      description: Paste your `docker run` command or `docker-compose.yml` (remove any sensitive values).
+      render: shell
+    validations:
+      required: true
+
+  - type: input
+    id: image-tag
+    attributes:
+      label: Image tag
+      description: Which Docker image tag are you using?
+      placeholder: "e.g. latest, 1.11.0"
+    validations:
+      required: true
+
+  - type: dropdown
+    id: platform
+    attributes:
+      label: Platform
+      options:
+        - AMD64 (Intel/AMD)
+        - ARM64 (Apple Silicon, Raspberry Pi)
+    validations:
+      required: true
+
+  - type: input
+    id: browser
+    attributes:
+      label: Browser
+      placeholder: "e.g. Chrome 130, Firefox 133, Safari 18"
+
+  - type: textarea
+    id: logs
+    attributes:
+      label: Logs
+      description: Paste any relevant container logs (`docker logs <container>`).
+      render: shell
+
+  - type: textarea
+    id: screenshots
+    attributes:
+      label: Screenshots
+      description: If applicable, add screenshots to help explain the problem.

.github/ISSUE_TEMPLATE/config.yml

@@ -0,0 +1,8 @@
+blank_issues_enabled: false
+contact_links:
+  - name: Documentation
+    url: https://stirling-image.github.io/stirling-image/
+    about: Check the docs for setup guides, configuration, and API reference.
+  - name: Security vulnerability
+    url: https://github.com/stirling-image/stirling-image/security/advisories/new
+    about: Report security issues privately through GitHub Security Advisories.

.github/ISSUE_TEMPLATE/feature_request.yml

@@ -0,0 +1,45 @@
+name: Feature Request
+description: Suggest a new tool, improvement, or change
+labels: ["enhancement"]
+body:
+  - type: checkboxes
+    id: checklist
+    attributes:
+      label: Before submitting
+      options:
+        - label: I searched existing issues and didn't find a duplicate
+          required: true
+
+  - type: textarea
+    id: problem
+    attributes:
+      label: Problem
+      description: What problem does this solve? Describe the use case or frustration.
+      placeholder: |
+        I frequently need to convert AVIF files to JPEG, but there's no tool for it.
+        I currently have to use an external service which means my images leave my machine.
+    validations:
+      required: true
+
+  - type: textarea
+    id: solution
+    attributes:
+      label: Proposed solution
+      description: How do you think this should work?
+      placeholder: |
+        Add an AVIF option to the format conversion tool, similar to how
+        HEIC and WebP are already supported.
+    validations:
+      required: true
+
+  - type: textarea
+    id: alternatives
+    attributes:
+      label: Alternatives considered
+      description: Have you tried any workarounds? Are there other approaches that could work?
+
+  - type: textarea
+    id: context
+    attributes:
+      label: Additional context
+      description: Screenshots, links, examples, or anything else that helps explain the request.