Add /log page that displays server log

This will eventually be behind an authorization guard so that only I
have access, but it's useful to have for monitoring and testing out
turbo streams.

Cargo.lock

@@ -260,6 +260,7 @@ dependencies = [
  "feed-rs",
  "maud",
  "notify",
+ "once_cell",
  "reqwest",
  "serde",
  "serde_with",
@@ -270,6 +271,7 @@ dependencies = [
  "tower-http",
  "tower-livereload",
  "tracing",
+ "tracing-appender",
  "tracing-subscriber",
  "validator",
 ]
@@ -2139,6 +2141,17 @@ dependencies = [
  "tracing-core",
 ]
 
+[[package]]
+name = "tracing-appender"
+version = "0.2.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "09d48f71a791638519505cefafe162606f706c25592e4bde4d97600c0195312e"
+dependencies = [
+ "crossbeam-channel",
+ "time 0.3.21",
+ "tracing-subscriber",
+]
+
 [[package]]
 name = "tracing-attributes"
 version = "0.1.24"