Rename the app from tracker to fit

The directory, the repo and the hostname are all fit; the module path,
the image, the namespace and the data file were still tracker. Nothing
is deployed yet, so this is free now and would not be later.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

README.md

@@ -1,4 +1,4 @@
-# tracker
+# fit
 
 A 75-day challenge, five things a day: the workout, the protein, the calories,
 the water, and three lines of gratitude.
@@ -40,7 +40,7 @@ faces for everything else, so there are no web fonts to serve.
 Needs Go 1.26. No database.
 
 ```sh
-export DATA_PATH="$PWD/data/tracker.json"
+export DATA_PATH="$PWD/data/fit.json"
 export TZ_NAME="America/Los_Angeles"
 
 go run ./cmd/server
@@ -57,7 +57,7 @@ go test ./...
 
 | Variable | Required | Notes |
 | --- | --- | --- |
-| `DATA_PATH` | no | The log file. Default `data/tracker.json`, relative to the working directory. The directory is created if missing. |
+| `DATA_PATH` | no | The log file. Default `data/fit.json`, relative to the working directory. The directory is created if missing. |
 | `TZ_NAME` | no | Default `America/Los_Angeles`. Decides when the day rolls over; a wrong value files entries against the wrong date. |
 | `BASE_URL` | no | Public origin. Default `http://localhost:8080`. |
 | `ADDR` | no | Listen address, default `:8080`. |
@@ -76,8 +76,8 @@ guarding the log, so pick a real password:
 
 ```sh
 htpasswd -nbB scott 'a-real-password' > /tmp/users
-kubectl create namespace tracker
-kubectl create secret generic tracker-basic-auth -n tracker --from-file=users=/tmp/users
+kubectl create namespace fit
+kubectl create secret generic fit-basic-auth -n fit --from-file=users=/tmp/users
 rm /tmp/users
 ```
 
@@ -87,7 +87,7 @@ existing `scottyah-tls` secret.
 To pull a copy of the log without the browser:
 
 ```sh
-kubectl exec -n tracker deploy/tracker-dep -- cat /data/tracker.json > tracker.json
+kubectl exec -n fit deploy/fit-dep -- cat /data/fit.json > fit.json
 ```
 
 ## Notes on how it's built