feat: forward durationWeeks from course.json to the deploy payload

[TheGupta2012]

Summary of changes

qBraid/qbraid-api#1135 adds an optional durationWeeks field (author-declared course length in weeks, integer 1 to 52) to the course document. This action was silently dropping it: the validate step rewrites the deploy payload via Course.model_dump(), and pydantic ignores fields the model does not declare, so nothing extra in course.json ever reached the API.

• Course model gains durationWeeks: Optional[int] = Field(None, ge=1, le=52) — the same bounds the API enforces, so a bad value fails validation with a clear field-level message instead of a 400 at deploy time.
• The payload is dumped as-is: a course.json without the field serializes it as null, and qbraid-api#1135 treats an explicit null the same as an absent field, so no key-stripping is needed here.
• Tests: declared value survives into the payload; absent field serializes as null; 0, -3, 53, 2.5 and "two" fail validation.

Validation run: full unit suite (171 passed, rerun after the null simplification), make format-check (clean). make lint-check fails identically on unmodified main (pre-existing findings in untouched files; none introduced here).

Coordinated PRs

• qBraid/qbraid-api#1135 — adds and validates the field (merge first; until it is live, a forwarded field is stripped harmlessly by the API's request validation).
• qBraid/qbraid-account#741 — displays it on catalog cards.
• qBraid/Quantum-Club-Thailand#12 — declares values in the course specs. Without this action PR those spec values never reach the API, since the Thailand workflow pins upload-course-action@main. No Thailand-side change needed once this merges.

Merge order: qbraid-api#1135 first, then this, then deploy the courses. Violations degrade gracefully: this PR before the API change forwards a field the API strips; specs deployed before this PR keep today's guessed labels.

🤖 Generated with Claude Code

[rryoung98]

Ran this branch for real from a qBraid-tutorial workflow into the pr-741 preview API (create and update mode) and locally against 0, 53, 2.5, "two", null, absent, 1 and 52; all behaved as described. Pushed 1420762: durationWeeks is now strict=True, because pydantic's lax mode coerced "3" to 3 and forwarded a value the API rejects with 400. Test parametrization and changelog updated.

Unrelated but you will hit it: the documented "Stage 0: validate API key" is not wired into action.yml, so an expired key only surfaces after validation, notebook and image stages have run.