fix: project finished backup jobs onto host row + smoke path tweaks

The dashboard's 'Last backup' column reads hosts.last_backup_at /
last_backup_status, but the WS handler only updated hosts.repo_status
on job.finished — backup terminations were silently dropped. Add a
SetHostLastBackup store method and call it from the same job.finished
switch that already handles init jobs.

Also: CLAUDE.md restage block uses /tmp/rm-smoke (the original
default) but the actual dev env runs out of $HOME/smoke. Update the
paths in the doc to match.

CLAUDE.md

@@ -38,7 +38,7 @@ but the **agent** is fetched by the install script from the server's
 **install script** are fetched from `<DataDir>/install/`. Plain
 `make build` doesn't touch any of those — the source-of-truth files
 in the working tree (`deploy/install/*`, `bin/restic-manager-agent`)
-must be copied into `/tmp/rm-smoke/data/...` *and* the running agent
+must be copied into `$HOME/smoke/data/...` *and* the running agent
 on this dev host needs replacing if the change touches agent code or
 the unit file.
 
@@ -53,13 +53,13 @@ asking the operator to test.**
 ```sh
 # 1. Restage what the install script serves (binary + unit + script).
 cp bin/restic-manager-agent \
-   /tmp/rm-smoke/data/agent-binaries/restic-manager-agent-linux-amd64
+   $HOME/smoke/data/agent-binaries/restic-manager-agent-linux-amd64
 cp deploy/install/install.sh \
-   /tmp/rm-smoke/data/install/install.sh
+   $HOME/smoke/data/install/install.sh
 cp deploy/install/install.ps1 \
-   /tmp/rm-smoke/data/install/install.ps1
+   $HOME/smoke/data/install/install.ps1
 cp deploy/install/restic-manager-agent.service \
-   /tmp/rm-smoke/data/install/restic-manager-agent.service
+   $HOME/smoke/data/install/restic-manager-agent.service
 
 # 2. Replace the running agent on this dev box and restart the
 #    service. Skip only when the change is server-side only AND
@@ -74,11 +74,11 @@ sudo -n systemctl restart restic-manager-agent
 # 3. The server runs from the working tree; restart it manually
 #    after a build that touches server code:
 pkill -f restic-manager-server
-RM_LISTEN=:8080 RM_DATA_DIR=/tmp/rm-smoke/data \
+RM_LISTEN=:8080 RM_DATA_DIR=$HOME/smoke/data \
 RM_BASE_URL=http://127.0.0.1:8080 \
-RM_SECRET_KEY_FILE=/tmp/rm-smoke/data/secret.key \
+RM_SECRET_KEY_FILE=$HOME/smoke/data/secret.key \
 RM_COOKIE_SECURE=false \
-./bin/restic-manager-server >> /tmp/rm-smoke/server.log 2>&1 &
+./bin/restic-manager-server >> $HOME/smoke/server.log 2>&1 &
 ```
 
 A `make smoke-deploy` target that bundles all of this would be a