fix: resolve 4 tag-blocking issues for v0.1.0

- README/CONTRIBUTING quick start: add UPTOP_ADMIN_KEY so SSH works on
  fresh DB, fix single-file go run path that doesn't compile
- apply --dry-run: assign placeholder IDs for new alerts and groups so
  resolveAlertID succeeds when monitors reference not-yet-created alerts
- deploy/*.yml: switch user-facing compose files from broken build
  context to image: lerkolabs/uptop:latest, fix dev context to ..

README.md

@@ -53,14 +53,14 @@ Canonical repo: [gitea.lerkolabs.com/lerkolabs/uptop](https://gitea.lerkolabs.co
 ## Quick start
 
 ```bash
-go run ./cmd/uptop
+UPTOP_ADMIN_KEY="$(cat ~/.ssh/id_ed25519.pub)" go run ./cmd/uptop
 ssh -p 23234 localhost
 ```
 
 Want some data to look at first:
 
 ```bash
-go run ./cmd/uptop -demo
+UPTOP_ADMIN_KEY="$(cat ~/.ssh/id_ed25519.pub)" go run ./cmd/uptop -demo
 ```
 
 ## Install