docs: update Loki queries from host to hostname label

Update all LogQL examples, agent instructions, and scripts to use
the hostname label instead of host, matching the Prometheus label
naming convention. Also update pipe-to-loki and bootstrap scripts
to push hostname instead of host.

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

docs/host-creation.md

@@ -50,7 +50,7 @@ homelab.host.tier = "test";  # or "prod"
 During the bootstrap process, status updates are sent to Loki. Query bootstrap logs with:
 
 ```
-{job="bootstrap", host="<hostname>"}
+{job="bootstrap", hostname="<hostname>"}
 ```
 
 ### Bootstrap Stages
@@ -72,7 +72,7 @@ The bootstrap process reports these stages via the `stage` label:
 
 ```
 # All bootstrap activity for a host
-{job="bootstrap", host="myhost"}
+{job="bootstrap", hostname="myhost"}
 
 # Track all failures
 {job="bootstrap", stage="failed"}
@@ -87,7 +87,7 @@ Once the VM reboots with its full configuration, it will start publishing metric
 
 1. Check bootstrap completed successfully:
    ```
-   {job="bootstrap", host="<hostname>", stage="success"}
+   {job="bootstrap", hostname="<hostname>", stage="success"}
    ```
 
 2. Verify the host is up and reporting metrics:
@@ -102,7 +102,7 @@ Once the VM reboots with its full configuration, it will start publishing metric
 
 4. Check logs are flowing:
    ```
-   {host="<hostname>"}
+   {hostname="<hostname>"}
    ```
 
 5. Confirm expected services are running and producing logs
@@ -119,7 +119,7 @@ Once the VM reboots with its full configuration, it will start publishing metric
 
 1. Check bootstrap logs in Loki - if they never progress past `building`, the rebuild likely consumed all resources:
    ```
-   {job="bootstrap", host="<hostname>"}
+   {job="bootstrap", hostname="<hostname>"}
    ```
 
 2. **USER**: SSH into the host and check the bootstrap service:
@@ -149,7 +149,7 @@ Usually caused by running the `create-host` script without proper credentials, o
 
 2. Check bootstrap logs for vault-related stages:
    ```
-   {job="bootstrap", host="<hostname>", stage=~"vault.*"}
+   {job="bootstrap", hostname="<hostname>", stage=~"vault.*"}
    ```
 
 3. **USER**: Regenerate and provision credentials manually: