template2: send bootstrap status to Loki for remote monitoring

Adds log_to_loki function that pushes structured log entries to Loki
at key bootstrap stages (starting, network_ok, vault_*, building,
success, failed). Enables querying bootstrap state via LogQL without
console access.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

hosts/template2/bootstrap.nix

@@ -6,6 +6,43 @@ let
     text = ''
       set -euo pipefail
 
+      LOKI_URL="http://monitoring01.home.2rjus.net:3100/loki/api/v1/push"
+
+      # Send a log entry to Loki with bootstrap status
+      # Usage: log_to_loki <stage> <message>
+      # Fails silently if Loki is unreachable
+      log_to_loki() {
+        local stage="$1"
+        local message="$2"
+        local timestamp_ns
+        timestamp_ns="$(date +%s)000000000"
+
+        local payload
+        payload=$(jq -n \
+          --arg host "$HOSTNAME" \
+          --arg stage "$stage" \
+          --arg branch "''${BRANCH:-master}" \
+          --arg ts "$timestamp_ns" \
+          --arg msg "$message" \
+          '{
+            streams: [{
+              stream: {
+                job: "bootstrap",
+                host: $host,
+                stage: $stage,
+                branch: $branch
+              },
+              values: [[$ts, $msg]]
+            }]
+          }')
+
+        curl -s --connect-timeout 2 --max-time 5 \
+          -X POST \
+          -H "Content-Type: application/json" \
+          -d "$payload" \
+          "$LOKI_URL" >/dev/null 2>&1 || true
+      }
+
       echo "================================================================================"
       echo "                     NIXOS BOOTSTRAP IN PROGRESS"
       echo "================================================================================"
@@ -14,19 +51,27 @@ let
       # Read hostname set by cloud-init (from Terraform VM name via user-data)
       # Cloud-init sets the system hostname from user-data.txt, so we read it from hostnamectl
       HOSTNAME=$(hostnamectl hostname)
+      # Read git branch from environment, default to master
+      BRANCH="''${NIXOS_FLAKE_BRANCH:-master}"
+
       echo "Hostname: $HOSTNAME"
       echo ""
       echo "Starting NixOS bootstrap for host: $HOSTNAME"
+
+      log_to_loki "starting" "Bootstrap starting for $HOSTNAME (branch: $BRANCH)"
+
       echo "Waiting for network connectivity..."
 
       # Verify we can reach the git server via HTTPS (doesn't respond to ping)
       if ! curl -s --connect-timeout 5 --max-time 10 https://git.t-juice.club >/dev/null 2>&1; then
         echo "ERROR: Cannot reach git.t-juice.club via HTTPS"
         echo "Check network configuration and DNS settings"
+        log_to_loki "failed" "Network check failed - cannot reach git.t-juice.club"
         exit 1
       fi
 
       echo "Network connectivity confirmed"
+      log_to_loki "network_ok" "Network connectivity confirmed"
 
       # Unwrap Vault token and store AppRole credentials (if provided)
       if [ -n "''${VAULT_WRAPPED_TOKEN:-}" ]; then
@@ -55,6 +100,7 @@ let
           chmod 600 /var/lib/vault/approle/secret-id
 
           echo "Vault credentials unwrapped and stored successfully"
+          log_to_loki "vault_ok" "Vault credentials unwrapped and stored"
         else
           echo "WARNING: Failed to unwrap Vault token"
           if [ -n "$UNWRAP_RESPONSE" ]; then
@@ -68,17 +114,17 @@ let
           echo "To regenerate token, run: create-host --hostname $HOSTNAME --force"
           echo ""
           echo "Vault secrets will not be available, but continuing bootstrap..."
+          log_to_loki "vault_warn" "Failed to unwrap Vault token - continuing without secrets"
         fi
       else
         echo "No Vault wrapped token provided (VAULT_WRAPPED_TOKEN not set)"
         echo "Skipping Vault credential setup"
+        log_to_loki "vault_skip" "No Vault token provided - skipping credential setup"
       fi
 
       echo "Fetching and building NixOS configuration from flake..."
-
-      # Read git branch from environment, default to master
-      BRANCH="''${NIXOS_FLAKE_BRANCH:-master}"
       echo "Using git branch: $BRANCH"
+      log_to_loki "building" "Starting nixos-rebuild boot"
 
       # Build and activate the host-specific configuration
       FLAKE_URL="git+https://git.t-juice.club/torjus/nixos-servers.git?ref=$BRANCH#''${HOSTNAME}"
@@ -86,12 +132,14 @@ let
       if nixos-rebuild boot --flake "$FLAKE_URL"; then
         echo "Successfully built configuration for $HOSTNAME"
         echo "Rebooting into new configuration..."
+        log_to_loki "success" "Build successful - rebooting into new configuration"
         sleep 2
         systemctl reboot
       else
         echo "ERROR: nixos-rebuild failed for $HOSTNAME"
         echo "Check that flake has configuration for this hostname"
         echo "Manual intervention required - system will not reboot"
+        log_to_loki "failed" "nixos-rebuild failed - manual intervention required"
         exit 1
       fi
     '';