feat: Python supervisor + feature flags

Supervisor (replaces supervisor.sh):
- supervisor.py — cron-based pipeline orchestration, reads workflows.toml
  on every tick, runs due extractors in topological waves with parallel
  execution, then SQLMesh transform + serving export
- workflows.toml — workflow registry: overpass (monthly), eurostat (monthly),
  playtomic_tenants (weekly), playtomic_availability (daily),
  playtomic_recheck (hourly 6–23)
- padelnomics-supervisor.service — updated ExecStart to Python supervisor

Extraction enhancements:
- proxy.py — optional round-robin/sticky proxy rotation via PROXY_URLS env
- playtomic_availability.py — parallel fetch (EXTRACT_WORKERS), recheck mode
  (main_recheck) re-queries imminent slots for accurate occupancy measurement
- _shared.py — realistic browser User-Agent on all extractor sessions
- stg_playtomic_availability.sql — reads morning + recheck snapshots, tags each
- fct_daily_availability.sql — prefers recheck over morning for same slot

Feature flags (replaces WAITLIST_MODE env var):
- migration 0019 — feature_flags table, 5 initial flags:
  markets (on), payments/planner_export/supplier_signup/lead_unlock (off)
- core.py — is_flag_enabled() + feature_gate() decorator
- routes — payments, markets, planner_export, supplier_signup, lead_unlock gated
- admin flags UI — /admin/flags toggle page + nav link
- app.py — flag() injected as Jinja2 global

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

extract/padelnomics_extract/pyproject.toml

@@ -14,6 +14,7 @@ extract-overpass = "padelnomics_extract.overpass:main"
 extract-eurostat = "padelnomics_extract.eurostat:main"
 extract-playtomic-tenants = "padelnomics_extract.playtomic_tenants:main"
 extract-playtomic-availability = "padelnomics_extract.playtomic_availability:main"
+extract-playtomic-recheck = "padelnomics_extract.playtomic_availability:main_recheck"
 
 [build-system]
 requires = ["hatchling"]