feat: named proxy pools with per-listener assignment

Add proxy_pools: top-level config (dict of name -> pool config) so
listeners can draw from different proxy sources. Each pool has
independent sources, health testing, state persistence, and refresh
cycles.

- PoolSourceConfig gains mitm: bool|None for API ?mitm=0/1 filtering
- ListenerConfig gains pool_name for named pool assignment
- ProxyPool gains name param with prefixed log messages and
  per-name state file derivation (pool-{name}.json)
- server.py replaces single proxy_pool with proxy_pools dict,
  validates listener pool references at startup, per-listener closure
- API /pool merges all pools (with pool field on multi-pool entries),
  /status and /config expose per-pool summaries
- Backward compat: singular proxy_pool: registers as "default"

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

config/example.yaml

@@ -20,14 +20,37 @@ chain:
   # - socks4://proxy:1080            # post-Tor SOCKS4/4a proxy
   # - http://user:pass@proxy:8080    # post-Tor HTTP CONNECT proxy
 
-# Managed proxy pool -- fetches from multiple sources, health-tests,
-# and rotates alive proxies per-connection after the static chain.
+# Named proxy pools -- each pool has its own sources, health tests,
+# and state file. Listeners reference pools by name via the "pool:" key.
+#
+# proxy_pools:
+#   clean:                            # MITM-free proxies
+#     sources:
+#       - url: http://10.200.1.250:8081/proxies/all
+#         mitm: false                 # filter: mitm=0 query param
+#     state_file: /data/pool-clean.json
+#     refresh: 300
+#     test_interval: 120
+#     test_timeout: 8
+#     max_fails: 3
+#   mitm:                             # MITM-capable proxies
+#     sources:
+#       - url: http://10.200.1.250:8081/proxies/all
+#         mitm: true                  # filter: mitm=1 query param
+#     state_file: /data/pool-mitm.json
+#     refresh: 300
+#     test_interval: 120
+#     test_timeout: 8
+#     max_fails: 3
+
+# Single proxy pool (legacy, still supported -- becomes pool "default"):
 # proxy_pool:
 #   sources:
 #     - url: http://10.200.1.250:8081/proxies
 #       proto: socks5        # optional: filter by protocol
 #       country: US          # optional: filter by country
 #       limit: 1000          # optional: max proxies to fetch
+#       mitm: false          # optional: filter by MITM status (true/false)
 #     - file: /etc/s5p/proxies.txt  # text file, one proxy URL per line
 #   refresh: 300             # re-fetch sources interval (seconds)
 #   test_interval: 120       # health test cycle interval (seconds)
@@ -59,26 +82,36 @@ chain:
 #   - socks5://10.200.1.250:9050
 #   - socks5://10.200.1.13:9050
 
-# Multi-listener mode -- each listener gets its own address and chain.
-# The "pool" keyword in a chain appends a random alive proxy from the pool.
+# Multi-listener mode -- each listener gets its own address, chain,
+# and optional pool assignment. The "pool" keyword in a chain appends
+# a random alive proxy from the named pool (or "default" if unnamed).
 # Multiple "pool" entries = multiple pool hops (deeper chaining).
 #
 # listeners:
 #   - listen: 0.0.0.0:1080
+#     pool: clean                        # draw from "clean" pool
 #     chain:
 #       - socks5://127.0.0.1:9050
-#       - pool                           # Tor + 2 random pool proxies
+#       - pool                           # Tor + 2 clean pool proxies
 #       - pool
 #
 #   - listen: 0.0.0.0:1081
+#     pool: clean
 #     chain:
 #       - socks5://127.0.0.1:9050
-#       - pool                           # Tor + 1 random pool proxy
+#       - pool                           # Tor + 1 clean pool proxy
 #
 #   - listen: 0.0.0.0:1082
 #     chain:
 #       - socks5://127.0.0.1:9050       # Tor only (no pool hops)
 #
+#   - listen: 0.0.0.0:1083
+#     pool: mitm                         # draw from "mitm" pool
+#     chain:
+#       - socks5://127.0.0.1:9050
+#       - pool                           # Tor + 2 MITM pool proxies
+#       - pool
+#
 # When using "listeners:", the top-level "listen" and "chain" keys are ignored.
 # If "listeners:" is absent, the old format is used (single listener).