fix(web): repair news ticker custom-feeds save for JSON path (#376)

* feat(install): surface root cause of web dependency install failures

install_dependencies_apt.py previously reported only which packages
failed, not why - the actual apt/pip error was discarded (apt) or
could scroll out of the on_error log tail (pip), leaving "Step 7:
Install web interface dependencies (line 915)" as the only visible
detail.

Capture command output for each install attempt and print a compact
DEPENDENCY INSTALLATION FAILURES summary with the last lines of error
output per package. Also run the installer with `python3 -u` for
real-time, correctly-ordered logging, and widen the on_error tail from
50 to 100 lines so the summary isn't cut off.

* fix(web): repair news ticker custom-feeds save for JSON path

The JS dotToNested() helper converts indexed form fields like
feeds.custom_feeds.0.name into a dict {'0': {name:...}} rather than a
proper array. The form-data path already had fix_array_structures() to
convert those dicts back to arrays before schema validation, but the
JSON path (used by all web-UI saves) never ran that fix, so saving any
custom feed produced a schema validation error: "Expected type array,
got object".

Add _fix_json_arrays() immediately after schema loading on the JSON
path, mirroring the existing fix_array_structures() logic.

Also fix custom-feeds.js getValue() to omit the logo key entirely when
no logo is present instead of returning logo:null, which would fail
schema validation (logo expects type object).

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

* fix(install,tools): address PR 376 review findings

- first_time_install.sh: add _clone_rpi_rgb() wrapper so retry() cleans
  up any partial rpi-rgb-led-matrix-master dir before each clone attempt
- first_time_install.sh: use apt-get -o DPkg::Lock::Timeout=180 so apt
  handles lock contention natively instead of relying solely on flock TOCTOU check
- install_dependencies_apt.py: pass DPkg::Lock::Timeout=180 to apt-get
  install to avoid failing when unattended-upgrades holds the lock
- install_dependencies_apt.py: add type annotations to all public helpers
- api_v3.py: fix install_plugin_requirements to read plugin_manager from
  api_v3 blueprint attribute instead of the always-None module variable
- tools.html: loadGitInfo() now checks r.ok before parsing JSON and
  surfaces d.status === 'error' with the server's message in the panel

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

* fix(tools,api): address three additional review findings

- api_v3.py install_plugin_requirements: replace hardcoded plugin-repos
  fallback with config-driven resolution (plugin_system.plugins_directory),
  matching the pattern used elsewhere in the module
- api_v3.py _fix_json_arrays: recurse into converted and existing array
  elements when items.type is object, so nested numeric-keyed dicts inside
  array items are also normalized
- tools.html toolsAction: check r.ok before r.json() and recover
  gracefully from non-JSON error bodies (HTML 500 pages), consistent
  with the existing loadGitInfo guard

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

---------

Co-authored-by: Chuck <chuck@example.com>
Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>

web_interface/static/v3/js/widgets/custom-feeds.js

@@ -54,15 +54,18 @@
                 const logoIdInput = row.querySelector('input[name*=".logo.id"]');
                 
                 if (nameInput && urlInput) {
-                    feeds.push({
+                    const feedObj = {
                         name: nameInput.value,
                         url: urlInput.value,
-                        enabled: enabledInput ? enabledInput.checked : true,
-                        logo: logoPathInput || logoIdInput ? {
+                        enabled: enabledInput ? enabledInput.checked : true
+                    };
+                    if (logoPathInput || logoIdInput) {
+                        feedObj.logo = {
                             path: logoPathInput ? logoPathInput.value : '',
                             id: logoIdInput ? logoIdInput.value : ''
-                        } : null
-                    });
+                        };
+                    }
+                    feeds.push(feedObj);
                 }
             });