compliance: flag-gate AI portfolio + cloud sync + Stripe; de-risk prompts; harden reviewer

Implements docs/read-markets-compliance-changes.md as flag-gated changes
(no deletions) so paused features stay in the tree for future re-enable.
All four flags default False so a fresh deploy is compliance-safe.

- New env flags: PORTFOLIO_AI_ENABLED, PORTFOLIO_SYNC_ENABLED,
  TICKER_UNIVERSE_AGGREGATE_ENABLED, SUBSCRIPTIONS_ENABLED.
- Gates: /api/analyze, /api/portfolio/sync*, /api/stripe/*, /pricing,
  ticker_universe writes, portfolio_analysis.analyse(). is_paid_active()
  returns True for any auth'd user when subscriptions are paused.
- Prompts (PROMPT_VERSION 10): universal _COMPLIANCE_RIDER prepended to
  every system prompt; watch list removed; price-target / close-above-below
  / trigger / forward-state-as-description rules added; SPECULATIVE
  pivoted to regime-only scenarios; daily + weekly digests tightened.
- Reviewer: deterministic regex/lexicon pre-check fail-closed under the
  Haiku call; portfolio rider gated by PORTFOLIO_AI_ENABLED; base prompt
  sharpened for forward-state and MAR forward-opinion patterns;
  ReviewerVerdict audit table; generate_with_review retry helper.
- Migration 0026: purge portfolio_sync + ticker_universe; create
  reviewer_verdicts.
- Copy: MAR cite fixed to Art 3(1)(35) + Art 20 + Del Reg 2016/958;
  portfolio reframed as browser-only viewer in disclaimer / privacy /
  terms / about / pricing / landing (en + it). TODO(legal) marker for
  lawyer sign-off on disclaimer.
- Tests: 13 lexicon + 6 reviewer compliance regressions; conftest enables
  all flags so existing 402 tests still cover their code paths.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

app/templates/public_base.html

@@ -36,7 +36,9 @@
       {{ BRAND_NAME }}
     </a>
     <nav class="public-header__nav">
+      {% if SUBSCRIPTIONS_ENABLED %}
       <a href="/pricing" class="{% if request.url.path == '/pricing' %}active{% endif %}">Pricing</a>
+      {% endif %}
       <a href="/about"   class="{% if request.url.path == '/about'   %}active{% endif %}">About</a>
       {# Lang switch — currently only the landing page opts in
          (lang_switch=true). When other public pages get translated
@@ -66,7 +68,7 @@
         <span class="public-footer__tagline">{{ TAGLINE }}</span>
       </div>
       <nav class="public-footer__links">
-        <a href="/pricing">Pricing</a>
+        {% if SUBSCRIPTIONS_ENABLED %}<a href="/pricing">Pricing</a>{% endif %}
         <a href="/about">About</a>
         <a href="/terms">Terms</a>
         <a href="/privacy">Privacy</a>