Phase 14b-2: BasicTheme rewritten on iManager 2.0 stack

[bigin]

The bundled basic theme now extends Frontend\Site and pulls every service from the container — no remaining call into the legacy imanager() function or editor/core/ classes survives the public render path. Pagination, theme cache, template fragments, navigation, archive, hero, contact and subscribe are all on 2.0 plumbing.

Key rewrites:

• BasicTheme (lib/Basic.php) extends Frontend\Site and overrides init()+render(). Article list / archive use the typed PageRepository methods (findInTimeRange, findByParent, countByParent), pagination is built with iManager's Pagination value object + PaginationRenderer. Single-article rendering forces template blog-post via currentTemplate() instead of mutating the Page DTO. Contact + subscribe + loadToken endpoints preserved as a bridge with the new typed Request accessors and JSON responses; CSRF placeholders are empty until 14c-1 wires auth back.
• BasicRouter (lib/BasicRouter.php) collapsed to a 22-line wrapper that dispatches actions and delegates routing to BasicTheme.
• _ext.php sets up BasicTheme + checks the FilesystemCache for a SuperCache hit before invoking the router.
• lib/subscriber/MailChimp.php: typed properties, removed dead Imanager\Util import, defensive defaults for missing config.

Frontend\Site additions for the theme surface:

• Properties: input (Imanager\Http\Request), templateParser (TemplateRenderer), cache (FilesystemCache), msgs[]
• currentTemplate() override hook for blog-style routing
• getBasePath(), getPageUrl() (cycle-safe), addMsg()
• init() empty hook for theme subclasses

Frontend\PageRepository additions:

• findByParent(parent, orderBy, direction, activeOnly, offset, limit)
• findInTimeRange(start, end, parent, orderBy, direction)
• countByParent(parent, activeOnly)
• levels(rootParent, maxDepth, activeOnly, excludeIds) with visited-set cycle detection (the migrated demo data has page id=8 pointing parent→8 to itself; would otherwise OOM the request)
• descendants(parent) with the same cycle guard

Theme files & data:

• resources/_tpls.php migrated from [[VAR]] to {{var}} so the iManager TemplateRenderer (Phase 11) resolves them; pagination fragments grouped under a pagination sub-array with the keys PaginationRenderer expects (wrapper/link/current/prev/...).
• data/settings/basic-theme-config.php: dropped the static Scriptor::getConfig() / BasicTheme::VERSION references that don't autoload on the 2.0 stack — BasicTheme::init() merges the live values from $site->config.
• template.php uses $site->currentTemplate() so the blog routing can override without mutating the Page DTO.
• index.php delegates to the theme's _ext.php when present and bails out cleanly when _ext.php returns early on a SuperCache hit.

Manual smoke (PHP built-in server):
GET / 200, 7.3 KB
GET /scriptors-demo-page 200, 7.5 KB (home alt)
GET /articles/ 200, 7.1 KB (article list)
GET /articles/page2/ 200, 5.8 KB (paginated)
GET /articles/get-started-with-scriptor 200, 7.7 KB (single article)
GET /contact 200, 7.1 KB (form)
GET /this-does-not-exist 404