feat: Implement pre and post survey phases

[vnthanhdng]

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[vnthanhdng]

Backend

• added phase: "pre" | "post" (default "post").
• createSurveyResponse now validates and stores phase; list/stats/export accept a phase filter; stats now group by phase and only count questions belonging to that phase; CSV exports include a Phase column.
• added getSurveyPhasePresence helper; updateUserProgress and batchUpdateUserProgress now accept preSurveyComplete/postSurveyComplete, merge with existing flags so single-phase updates don't clobber the other, and auto-satisfy a phase if the survey has no questions for it. All three Progress init sites seed {webinar, preSurvey, postSurvey, certificate}.

Frontend

• each question card has a Pre/Post select; new questions default to "post"; phase is sent when creating Question docs.
• takes a phase prop, filters questions by phase, sends phase on submit, sends phase-aware progress flags (pre → preSurveyComplete; post → postSurveyComplete + webinarComplete, preserving the previous side-effect), shows phase-specific empty state and title.
• split state into preSurveyCompleted / postSurveyCompleted (with legacy survey fallback for old progress docs), added a Pre-Survey tab before Workshop, renamed Survey → Post-Survey, both tabs reuse the same SurveyModal with a different phase prop.

note: existing Question/SurveyResponse/Progress docs default to "post" semantics, so already-completed courses continue to read as complete.