Replace deploy scripts with self-contained compose bootstrap jobs

Removes every wrapper script under deploy/ (up.ps1, up.sh, scripts/*,
zitadel/provision.*) and folds their logic into three one-shot services
in compose.yml, following the pattern already used by seaweedfs-init:

  keys-init     generates the RS256 stream-ticket key pair
  migrate       applies the EF Core migrations (backend/Musify.Migrator.Dockerfile)
  zitadel-init  creates the Musify project + OIDC apps, writes the client
                ids back into the active env file

Deploying is now two plain `docker compose` commands, no scripts to run
or chmod:

  docker compose -f deploy/compose.yml -f deploy/compose.dev.yml up -d
  docker compose -f deploy/compose.yml -f deploy/compose.dev.yml --profile apps up -d --build

(swap compose.dev.yml for compose.prod.yml + --env-file deploy/.env.prod
for production). The first command brings up infra and lets the bootstrap
jobs run to completion; the second builds and starts the apps, which by
then read real OIDC values instead of empty ones — compose interpolates
${VAR} once per invocation, so this can't collapse into a single command
without the apps reading their own config file at container start instead
of via compose env (out of scope here).

Also:
- DatabaseDesignTimeFactory now also reads Database__ConnectionString
  from the environment, and DesignSettings.json is optional, so the new
  migrate container works without user-secrets or a config file excluded
  from the Docker build context by .dockerignore.
- nginx's depends_on no longer lists the apps-profile services: it does
  not need them at its own startup (every vhost resolves its upstream at
  request time via the embedded Docker resolver), and requiring them made
  `compose.prod.yml up -d` (without --profile apps) an invalid project.
- env_get/env_set in zitadel-init strip \r: the mounted env file can have
  CRLF line endings on Windows, which otherwise makes an empty-looking
  value non-empty to `[ -z ... ]`. .env.example/.env.prod.example are
  pinned to LF via .gitattributes for the same reason. Also fixed:
  rewriting the bind-mounted env file in place instead of renaming a temp
  file over it (rename onto a bind-mounted inode fails with "Resource
  busy").
- Removed compose.share.yml and zitadel/.output-share/ — a "temporary"
  personal overlay that had leaked a real Zitadel service-account PAT
  into git history (committed in 70968b3). That token should be rotated.
- Removed deploy/.tmp/ from .gitignore: nothing mounts or creates it
  anymore (it never actually did, either — no compose service referenced
  it, only the now-removed up.ps1 did).

Verified end-to-end with Docker: a clean `down -v` + fresh `up -d` +
`--profile apps up -d --build` on the dev stack brings up all four one-shot
jobs successfully and all four apps healthy (api/gateway return 200,
worker starts its consumers with no errors, web-player responds). Also
verified compose.prod.yml starts nginx cleanly with dummy certs and no
apps running, confirming the depends_on fix.

deploy/compose.prod.yml

@@ -4,11 +4,13 @@ name: musify-prod
 # Nothing but nginx publishes a port; every other service is reachable only on
 # the internal `musify-prod_default` network.
 #
-#   docker compose --env-file deploy/.env.prod \
-#     -f deploy/compose.yml -f deploy/compose.prod.yml --profile apps up -d --build
+#   docker compose --env-file deploy/.env.prod -f deploy/compose.yml -f deploy/compose.prod.yml up -d
+#   docker compose --env-file deploy/.env.prod -f deploy/compose.yml -f deploy/compose.prod.yml --profile apps up -d --build
 #
-# Use ./up.sh, which also generates the stream keys, provisions Zitadel and
-# applies the database migrations.
+# The first command starts the infrastructure, the nginx edge and the
+# one-shot bootstrap jobs (stream keys, migrations, Zitadel project/apps); the
+# second builds and starts the applications, picking up the OIDC client ids
+# the first command just wrote into deploy/.env.prod. See deploy/README.md.
 
 services:
   worker:
@@ -16,14 +18,23 @@ services:
     volumes:
       - ./secrets:/secrets:ro
 
+  # zitadel-init (compose.yml) edits whichever env file is mounted here.
+  zitadel-init:
+    volumes:
+      - ./.env.prod:/workspace/.env
+
+  # Every vhost proxies through `set $upstream ...; proxy_pass $upstream;`
+  # with the embedded Docker DNS resolver (see nginx/templates), so nginx
+  # does not need api/gateway/web-player to exist at its own startup — only
+  # at request time. That is what lets it start in the FIRST command
+  # (profile-gated services aren't part of that invocation yet) and still be
+  # reachable at the auth domain for zitadel-init to provision through.
   nginx:
     image: nginx:1.27-alpine
     container_name: musify-nginx
     depends_on:
-      - api
-      - gateway
-      - zitadel
-      - web-player
+      zitadel:
+        condition: service_started
     environment:
       # The entrypoint renders /etc/nginx/templates/*.template with envsubst.
       # The filter keeps it from eating nginx's own $host / $remote_addr.