feat(learning): self-improving CMO with observe→analyze→propose→apply→measure loop

Ambitious scope: the CMO agent now learns from its own telemetry and tunes its tools every day without a code deploy.

Full details in the README 'Self-learning loop' section and in the commit body. Portal at /insights/, slash commands /cmo insights + /cmo learn, CLI cmoagent learn, scheduled daily cycle wired into the notifier loop.

• 18 files · +3800 lines
• 19 new tests (311/311 green)
• New DB migration (cmo_insights + cmo_dynamic_config + cmo_fitness_snapshots)
• Dynamic overlay for pitch_analyzer hot_keywords / saturated_genres