feat(gateway): sub-phase 5b-iii — intake policy configuration + session cookie

[FredericoAndrade]

Summary

• Session cookie — gateway_gated changed from 30-day to session-scoped; gate fires on every new browser session
• Named intake field sets — gateway_intake_fields filter now keyed by set name (e.g. 'standard') instead of post type slug; JS payload renamed intakeSteps → intakeSets
• IntakeResolver — new class implementing 3-tier resolution (per-record postmeta → per-CPT wp_option → global wp_option) for both the field set name and the always flag
• SettingsRepository — 4 new intake accessors + option key constants for global and per-CPT intake settings
• Admin UI — Settings page gains an "Intake forms" section (global set dropdown, global always select, per-CPT rows); resource metabox gains "Intake form" and "Show on repeat downloads" selects
• Download_Shortcode + meta--videos-single.php — all gateway download links now emit data-intake-set and data-intake-always attributes
• JS — openModal and doSilentPassthrough accept intake params; passthrough with intakeAlways=true shows the intake step instead of proceeding directly to download

Test plan

• composer test — 187 tests, 270 assertions, all green
• composer lint — clean
• Session cookie: download a gated file → gate appears → submit → download. Close browser entirely → reopen → click same link → gate appears again (not skipped)
• Passthrough within session: download a second file without closing the browser → gate skipped silently
• Intake set: register a named set via gateway_intake_fields filter, assign it to a CPT in Settings → Download Gateway → intake step appears after gate submit for that CPT
• Per-record override: set _gateway_intake_set = 'none' on one post in a CPT that has a default set → intake skipped for that post only
• Always flag: set "Show on repeat downloads = Yes" for a CPT → first download shows gate + intake; second download in same session (passthrough) still shows intake step
• data-intake-set and data-intake-always attributes visible in rendered HTML for shortcode links and video template links
• Settings page: "Intake forms" section renders correctly; saving persists values; per-CPT rows show inherit/set/always dropdowns

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