fix(install): remove weather and music credential stubs from secrets template

config_secrets.template.json shipped ledmatrix-weather and music as
top-level keys; config_manager deep-merges secrets into the main config
on load, so the reconciler treated them as plugin config entries and
auto-installed both plugins on first web UI visit after a fresh install.

Remove both keys from the template and clear the inline fallback block
in first_time_install.sh so new installs start clean.

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

config/config_secrets.template.json

@@ -1,17 +1,9 @@
 {
-    "ledmatrix-weather": {
-        "api_key": "YOUR_OPENWEATHERMAP_API_KEY"
-    },
     "youtube": {
         "api_key": "YOUR_YOUTUBE_API_KEY",
         "channel_id": "YOUR_YOUTUBE_CHANNEL_ID"
     },
-    "music": {
-        "SPOTIFY_CLIENT_ID": "YOUR_SPOTIFY_CLIENT_ID_HERE",
-        "SPOTIFY_CLIENT_SECRET": "YOUR_SPOTIFY_CLIENT_SECRET_HERE",
-        "SPOTIFY_REDIRECT_URI": "http://127.0.0.1:8888/callback"
-    },
     "github": {
         "api_token": "YOUR_GITHUB_PERSONAL_ACCESS_TOKEN"
     }
-} 
+}

first_time_install.sh

@@ -598,11 +598,7 @@ if [ ! -f "$PROJECT_ROOT_DIR/config/config_secrets.json" ]; then
     else
         echo "⚠ Template config/config_secrets.template.json not found; creating a minimal secrets file"
         cat > "$PROJECT_ROOT_DIR/config/config_secrets.json" <<'EOF'
-{
-  "weather": {
-    "api_key": "YOUR_OPENWEATHERMAP_API_KEY"
-  }
-}
+{}
 EOF
         # Check if service runs as root and set ownership accordingly
         SERVICE_USER="root"