Refactor installation and runner scripts for enhanced usability and security

- Updated the installation script to clarify that production wrappers do not include fixed test secrets, improving user guidance for local testing.
- Modified the jiggablend-manager and jiggablend-runner scripts to remove fixed test configurations, emphasizing the use of local test credentials via `make init-test`.
- Enhanced error handling in the runner script to ensure that an API key is provided, improving security and user feedback.
- Added new flags and options for the runner, including sandboxing capabilities and GPU ray tracing control, enhancing flexibility for users.
- Improved README documentation to reflect changes in usage and configuration, ensuring users have clear instructions for setup and execution.

web/templates/job_new.html

@@ -52,7 +52,7 @@
     </label>
     <div class="check-row">
       <label><input type="checkbox" id="unhide-objects" name="unhide_objects"> Unhide objects/collections</label>
-      <label><input type="checkbox" id="enable-execution" name="enable_execution"> Enable auto-execution in Blender</label>
+      <label><input type="checkbox" id="enable-execution" name="enable_execution" title="Allows Python drivers/scripts embedded in the .blend (--enable-autoexec). Job-bundled blender_addons/ always install automatically when present."> Allow .blend Python autoexec</label>
     </div>
     <button type="submit" class="btn primary">Create Job</button>
   </form>