add programmatic SEO content engine with article generation pipeline and tests

Adds a complete content generation system for producing SEO articles
at scale with embedded financial scenario widgets. Includes DB schema
(published_scenarios, article_templates, template_data, articles with
FTS5), bulk generation pipeline with staggered publish dates, admin CRUD
for templates/scenarios/articles, public markets hub with HTMX filtering,
catch-all article serving from pre-rendered static HTML, sitemap
integration, and 94 pytest tests covering the full stack.

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

CHANGELOG.md

@@ -6,6 +6,60 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/).
 
 ## [Unreleased]
 
+### Added — Programmatic SEO: Content Generation Engine
+- **Database migration 0010** — `published_scenarios`, `article_templates`,
+  `template_data`, `articles` tables with FTS5 full-text search on articles;
+  content-sync triggers for INSERT/UPDATE/DELETE
+- **Article template system** — parameterized content recipes with
+  `input_schema` (JSON field definitions), `url_pattern`, `title_pattern`,
+  `body_template` (Markdown + Jinja2); supports multiple content types
+  (only `calculator` built now)
+- **Template data rows** — per-city/region input data that feeds the
+  generation pipeline; manual add or bulk CSV upload
+- **Bulk generation pipeline** — `POST /admin/templates/<id>/generate`
+  computes financial scenarios from data rows via `validate_state()` +
+  `calc()`, renders Markdown with baked scenario cards, writes static HTML
+  to `data/content/_build/`, creates articles with staggered publish dates
+- **Published scenarios** — standalone financial widgets with pre-computed
+  `calc_json`; embeddable in articles via `[scenario:slug]` markers with
+  section variants (`:capex`, `:operating`, `:cashflow`, `:returns`, `:full`)
+- **Scenario widget templates** — 6 partial templates (summary, CAPEX
+  breakdown, revenue & OPEX, 5-year projection, returns & financing,
+  full combined) with dark navy header bar, Commit Mono numbers, responsive
+  metric grids, and "Try with your own numbers" CTA
+- **Static file rendering** — articles rendered to `data/content/_build/`
+  as pre-baked HTML; DB stores metadata only, no body content in DB
+- **Content blueprint** — catch-all route serves published articles by
+  `url_path`; registered last to avoid path collisions
+- **Markets hub** (`/markets`) — public search + country/region filter page
+  for discovering articles; HTMX live filtering via FTS5 queries
+- **Admin template CRUD** — list, create, edit, delete article templates;
+  view/add/upload/delete data rows; bulk generation form with start date
+  and articles-per-day controls
+- **Admin scenario CRUD** — list, create (with curated calculator form),
+  edit + recalculate, delete, preview all widget sections
+- **Admin article management** — list with status badges (draft/published/
+  scheduled), create manual articles (Markdown textarea), edit, delete,
+  publish/unpublish toggle, rebuild single or all articles
+- **Rebuild system** — `POST /admin/articles/<id>/rebuild` and
+  `/admin/rebuild-all` re-render article HTML from source (template+data
+  or markdown file) with fresh scenario `calc_json`
+- **Article detail page** — SEO meta tags (description, og:title,
+  og:description, og:type=article, og:image, canonical), article
+  typography styles, bottom CTA linking to planner
+- **Scenario widget CSS** — `.scenario-widget` component styles in
+  `input.css` with responsive table scroll and metric grid collapse;
+  `.article-body` typography for headings, paragraphs, lists, blockquotes,
+  tables, code blocks
+- **`slugify()` utility** — added to `core.py` for URL-safe slug generation
+- **`mistune` dependency** — Markdown → HTML rendering for articles
+- **Sitemap** — `/markets` and all published articles added to
+  `/sitemap.xml` (only articles with `published_at <= now`)
+- **Footer** — "Markets" link added to Product column
+- **Admin dashboard** — Templates, Scenarios, Articles quick-link buttons
+- **Path collision prevention** — `RESERVED_PREFIXES` validation rejects
+  article `url_path` values that conflict with existing routes
+
 ### Added
 - **Dev setup script** (`scripts/dev_setup.sh`) — interactive bootstrap that
   checks prerequisites, installs deps, creates `.env` with auto-generated