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>

infra/supervisor/workflows.toml

@@ -0,0 +1,33 @@
+# Workflow registry — the supervisor reads this file on every tick.
+# To add a new extractor: add a [section] here and create the Python module.
+#
+# Fields:
+#   module   — Python module path (must have a main() function)
+#   schedule — named preset ("hourly", "daily", "weekly", "monthly")
+#              or raw cron expression (e.g. "0 6-23 * * *")
+#   entry    — optional: function name if not "main" (default: "main")
+#   depends_on — optional: list of workflow names that must run first
+#   proxy_mode — optional: "round-robin" (default) or "sticky"
+
+[overpass]
+module = "padelnomics_extract.overpass"
+schedule = "monthly"
+
+[eurostat]
+module = "padelnomics_extract.eurostat"
+schedule = "monthly"
+
+[playtomic_tenants]
+module = "padelnomics_extract.playtomic_tenants"
+schedule = "weekly"
+
+[playtomic_availability]
+module = "padelnomics_extract.playtomic_availability"
+schedule = "daily"
+depends_on = ["playtomic_tenants"]
+
+[playtomic_recheck]
+module = "padelnomics_extract.playtomic_availability"
+entry = "main_recheck"
+schedule = "0 6-23 * * *"
+depends_on = ["playtomic_availability"]