Add argon2id documentation

src/docs/markdown/caddyfile/directives/basic_auth.md

@@ -26,7 +26,7 @@ basic_auth [<matcher>] [<hash_algorithm> [<realm>]] {
 }
 ```
 
-- **&lt;hash_algorithm&gt;** is the name of the password hashing algorithm (or KDF) used for the hashes in this configuration. Default: `bcrypt`
+- **&lt;hash_algorithm&gt;** specifies the password hashing algorithm (or key derivation function) used for the hashes in this configuration. Available options include `argon2id`, the default is `bcrypt`.
 
 - **&lt;realm&gt;** is a custom realm name.
 
@@ -64,3 +64,17 @@ example.com {
 }
 ```
 
+`argon2id` example
+
+```caddy
+example.com {
+	root * /srv
+
+	basic_auth /secret/* argon2id {
+		# Username "Bob", password "hiccup"
+		Bob $argon2id$v=19$m=47104,t=1,p=1$zJPvVe48N64JUa9MFlVhiw$b5Tznu0PxnA4TciY6qYe2BFPxncF1ePQaeNukHhH1cU
+	}
+
+	file_server
+}
+```

src/docs/markdown/command-line.md

@@ -251,11 +251,40 @@ Formats or prettifies a Caddyfile, then exits. The result is printed to stdout u
 
 Convenient way to hash a plaintext password. The resulting hash is written to stdout as a format usable directly in your Caddy config.
 
-`--plaintext` is the plaintext form of the password. If omitted, interactive mode will be assumed and the user will be shown a prompt to enter the password manually.
+`--plaintext`
+    The password to hash. If omitted, it will be read from stdin.
+    If Caddy is attached to a controlling TTY, the input will not be echoed.
 
-`--algorithm` may be `bcrypt` or any installed hash algorithm. Default is `bcrypt`.
+`--algorithm`
+    Selects the hashing algorithm. Valid options are:
+      * `argon2id` (recommended for modern security)
+      * `bcrypt`  (legacy, slower, configurable cost)
 
+bcrypt-specific parameters:
 
+`--bcrypt-cost`
+    Sets the bcrypt hashing difficulty. Higher values increase security by
+    making the hash computation slower and more CPU-intensive.
+    Must be within the valid range [bcrypt.MinCost, bcrypt.MaxCost].
+    If omitted or invalid, the default cost is used.
+
+Argon2id-specific parameters:
+
+`--argon2id-time`
+    Number of iterations to perform. Increasing this makes
+    hashing slower and more resistant to brute-force attacks.
+
+`--argon2id-memory`
+    Amount of memory to use during hashing.
+    Larger values increase resistance to GPU/ASIC attacks.
+
+`--argon2id-threads`
+    Number of CPU threads to use. Increase for faster hashing
+    on multi-core systems.
+
+`--argon2id-keylen`
+    Length of the resulting hash in bytes. Longer keys increase
+    security but slightly increase storage size.
 
 
 ### `caddy help`