refactor(settings): unify config.py, mconfig.py, and settings.py into single PrySettings

- Merge all configuration into settings.py with PRY_* env var prefix.
- Add legacy env aliases (PROXY_URL, TOR_ENABLED, MAX_RETRIES, etc.) for migration.
- Load and persist runtime overrides from JSON config file (default /app/config.json).
- Update scraper.py, deps.py, routers/config.py to use unified settings.
- Add resolved_proxy_chain and resolved_proxy_url properties.
- Replace tests/test_mconfig.py with tests/test_settings.py (9 tests).
- Update .env.example with new PRY_* options.
- All 500 tests pass; ruff clean.

deps.py

@@ -6,8 +6,6 @@ direct access to shared state.
 
 Usage:
     from deps import scraper, cache, automator, ...
-
-Part of Pry — https://git.rugmunch.io/RugMunchMedia/pryscraper
 """
 
 # SPDX-License-Identifier: MIT
@@ -19,18 +17,16 @@ from automator import PryAutomator
 from cache import ResponseCache
 from extractor import SchemaExtractor
 from jobqueue import JobQueue
-from mconfig import PryConfig
 from parser import DocumentParser
 from ratelimit import RateLimiter
 from scraper import PryScraper
-
-config = PryConfig()
+from settings import settings
 
 scraper = PryScraper()
 automator = PryAutomator()
 parser = DocumentParser()
 extractor = SchemaExtractor()
 cache = ResponseCache(capacity=1000)
-ratelimiter = RateLimiter(default_rpm=120, burst=200)
+ratelimiter = RateLimiter(default_rpm=settings.rate_limit_rpm, burst=200)
 queue = JobQueue()
 advanced = PryAdvanced(cache=cache)