Rewrite docs to not assume a local folder layout

The README previously described this stack as shared by "every project
under Documentos/", which is just this machine's local checkout location,
not something the repo itself should assume. Every project lives in its
own git repository; the path to this repo's checkout is a per-project
setting (ZITADEL_ADMIN_PAT_DIR), not a fixed convention.

Also drops leftover em dashes across the docs and compose comments for
plainer prose.

postgres-init/010-create-app-databases.sql

@@ -1,8 +1,8 @@
 -- Runs once, only on first init of the postgres_data volume.
 -- Zitadel provisions its own "zitadel" database itself, from the
--- ZITADEL_DATABASE_POSTGRES_ADMIN_* credentials in compose.yml — it does not
--- need to be created here. This script only creates the plain application
--- databases each project's own connection string points at.
+-- ZITADEL_DATABASE_POSTGRES_ADMIN_* credentials in compose.yml, so it does
+-- not need to be created here. This script only creates the plain
+-- application databases each project's own connection string points at.
 
 CREATE DATABASE musify_db;
 CREATE DATABASE ping_db;