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.

.env.example

@@ -69,3 +69,26 @@ PRY_FLARESOLVERR_URL=http://flaresolverr:8191/v1
 
 # ── Redis ──
 # PRY_REDIS_URL=redis://localhost:6379/0
+
+# ── Database ──
+# PRY_DATABASE_URL=postgresql+asyncpg://pry:pry@localhost/pry
+
+# ── Stealth ──
+# PRY_STEALTH_ENABLED=true
+# PRY_RANDOM_USER_AGENT=true
+# PRY_WEBDRIVER_OVERRIDE=true
+# PRY_CANVAS_NOISE=true
+# PRY_WEBRTC_DISABLE=true
+# PRY_GEOLOCATION_SPOOF=true
+# PRY_MIN_DELAY_MS=500
+# PRY_MAX_DELAY_MS=3000
+
+# ── Output ──
+# PRY_DEFAULT_FORMAT=markdown
+# PRY_MAX_CHARS=100000
+# PRY_INCLUDE_LINKS=true
+
+# ── x402 / MCP ──
+# PRY_X402_ENABLED=false
+# PRY_X402_PAY_TO=
+# PRY_MCP_ENABLED=true