feat: public rate-limited access for v1.1

Add PublicAccessListener (priority 84) that allows rate-limited
unauthenticated access to configured public paths. Authenticated users
bypass this listener entirely via AcceptListener/AllowListener.

New components:
- PublicPathMatcher service with wildcard path matching (* and **)
  and optional host-prefix scoping
- PublicAccessListener applying per-IP rate limiting to public paths
- Separate public_limiter compound rate limiter (burst + sustained)
- publicRateLimitCache pool (APCu in prod, array in tests)

New env vars:
- PUBLIC_PATHS (comma-separated path patterns, empty = disabled)
- PUBLIC_BURST_COUNT/PUBLIC_BURST_TIME (default 100/60s)
- PUBLIC_UPPER_COUNT/PUBLIC_UPPER_TIME (default 500/3600s)

Tests: 52 new tests (29 unit for PublicPathMatcher, 12 unit for
PublicAccessListener, 11 functional for PublicAccessFlowTest).
Total: 293 tests, 605 assertions, all passing.
PHP CS Fixer: 0 of 63 files need fixing.

Documentation: README, CHANGELOG, ROADMAP, Caddyfile, example.env
all updated with public access configuration and examples.

phpunit.dist.xml

@@ -22,6 +22,12 @@
         <!-- high rate limits so functional tests don't get blocked -->
         <server name="BURST_COUNT" value="10000" />
         <server name="UPPER_COUNT" value="10000" />
+        <!-- public access: enable for functional tests with low limits -->
+        <server name="PUBLIC_PATHS" value="/public/**" />
+        <server name="PUBLIC_BURST_COUNT" value="3" />
+        <server name="PUBLIC_BURST_TIME" value="60" />
+        <server name="PUBLIC_UPPER_COUNT" value="10000" />
+        <server name="PUBLIC_UPPER_TIME" value="3600" />
     </php>
 
     <testsuites>