chore(build): harden installer script and replace Makefile with Justfile

Stacked bottom of #701. Replaces Makefile with justfile and hardens install.sh (strict mode, logging, HTTP probes, curl -f on model downloads, no v0.10.1-beta fallback).

Closes #700.

.github/labeler.yml

@@ -29,7 +29,7 @@ ci:
   - changed-files:
       - any-glob-to-any-file:
           - ".github/**/*"
-          - "Makefile"
+          - "justfile"
           - "scripts/**/*"
           - ".flake8"
           - ".pre-commit-config.yaml"

.github/workflows/unified-pipeline.yml

@@ -38,7 +38,7 @@ jobs:
               - 'tests/**'
               - 'pyproject.toml'
               - 'requirements*.txt'
-              - 'Makefile'
+              - 'justfile'
               - '.pre-commit-config.yaml'
               - '.github/workflows/unified-pipeline.yml'
       - name: Check if website should deploy