feat: writing logs to the filesystem with rotation support (#1299)

* refactor: move lib/policy/config to lib/config

Signed-off-by: Xe Iaso <me@xeiaso.net>

* refactor: don't set global loggers anymore

Ref #864

You were right @kotx, it is a bad idea to set the global logger
instance.

Signed-off-by: Xe Iaso <me@xeiaso.net>

* feat(config): add log sink support

Signed-off-by: Xe Iaso <me@xeiaso.net>

* chore: update spelling

Signed-off-by: Xe Iaso <me@xeiaso.net>

* chore(test): go mod tidy

Signed-off-by: Xe Iaso <me@xeiaso.net>

* chore: update spelling

Signed-off-by: Xe Iaso <me@xeiaso.net>

* docs(admin/policies): add logging block documentation

Signed-off-by: Xe Iaso <me@xeiaso.net>

* docs: update CHANGELOG

Signed-off-by: Xe Iaso <me@xeiaso.net>

* fix(cmd/anubis): revert this change, it's meant to be its own PR

Signed-off-by: Xe Iaso <me@xeiaso.net>

* chore: go mod tidy

Signed-off-by: Xe Iaso <me@xeiaso.net>

* test: add file logging smoke test

Assisted-by: GLM 4.6 via Claude Code
Signed-off-by: Xe Iaso <me@xeiaso.net>

* fix: don't expose the old log file time format string

Signed-off-by: Xe Iaso <me@xeiaso.net>

---------

Signed-off-by: Xe Iaso <me@xeiaso.net>

test/log-file/anubis.yaml

@@ -0,0 +1,18 @@
+bots:
+  - name: challenge
+    user_agent_regex: CHALLENGE
+    action: CHALLENGE
+
+status_codes:
+  CHALLENGE: 200
+  DENY: 403
+
+logging:
+  sink: file
+  parameters:
+    file: "./var/anubis.log"
+    maxBackups: 3 # keep at least 3 old copies
+    maxBytes: 67108864 # each file can have up to 64 Mi of logs
+    maxAge: 7 # rotate files out every n days
+    compress: true
+    useLocalTime: false # timezone for rotated files is UTC