feat: Improve the initial setup experience

- Issue a single-use token for initial account creation
- Disable registration through other methods until the first account is made
- Print helpful instructions to the console on the first run
- Improve the welcome message sent in the admin room on first run

Cargo.toml

@@ -549,6 +549,12 @@ features = ["sync", "tls-rustls", "rustls-provider"]
 [workspace.dependencies.resolv-conf]
 version = "0.7.5"
 
+[workspace.dependencies.yansi]
+version = "1.0.1"
+
+[workspace.dependencies.askama]
+version = "0.14.0"
+
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 # Patches
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