feat(course): build out all 27 modules, capstone, scaffold, and conventions

Scaffold the course repo and author the full curriculum in dependency-chain
order, following the settled build decisions in handoff.md.

- Scaffold: course README, vendor-neutral AGENTS.md (dogfoods Module 5),
  _TEMPLATE.md (the fixed 9-section module shape), root .gitignore, ship config.
- Modules 1-2: reference exemplars (locked for tone/depth/lab style).
- Modules 3-27: full lessons + runnable labs, each following the template,
  respecting the chain, vendor/model-agnostic, with "feel the pain" labs.
- Module 8 hosting comparison web-researched and date-stamped (as of 2026-06-22),
  not written from memory; expansion-zone modules carry Verify-before-publish.
- Capstone: the full loop end to end on the running tasks-app example.

Lab code syntax-checked (Python/shell/YAML); every module has the 7 core
template sections.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01TfzV5QvtPDz8LJS3Pu5VLT

modules/15-security-scanning/lab/security-scan.sh

@@ -0,0 +1,48 @@
+#!/usr/bin/env bash
+#
+# security-scan.sh — the security gate for tasks-app (Module 15).
+#
+# Runs two scanners and exits non-zero if EITHER finds something. That non-zero exit is what turns
+# a CI run red (Module 14). One script, two homes: run it by hand for fast local feedback, and call
+# it from the pipeline so the same definition of "a finding" enforces the merge.
+#
+# These two tools (pip-audit, detect-secrets) are concrete examples of their categories — SCA and
+# secret scanning. Swap in any equivalent; keep the contract the same: scan, print, fail on findings.
+#
+# Usage:   ./security-scan.sh
+# Install: pip install pip-audit detect-secrets
+
+set -u  # treat unset vars as errors; we manage exit codes explicitly below.
+
+status=0
+
+echo "=== Gate 1: SCA / dependency scan (pip-audit) ==="
+if [ -f requirements.txt ]; then
+  if ! pip-audit -r requirements.txt; then
+    echo ">> SCA gate FAILED: unresolvable or vulnerable dependency. See above." >&2
+    status=1
+  fi
+else
+  echo "(no requirements.txt found — skipping SCA)"
+fi
+
+echo
+echo "=== Gate 2: secret scan (detect-secrets) ==="
+# detect-secrets prints a JSON report of any secrets it finds. We treat a non-empty results set as a
+# failure. `python -c` keeps this portable (no jq dependency).
+report="$(detect-secrets scan)"
+if printf '%s' "$report" | python -c 'import sys, json; sys.exit(0 if json.load(sys.stdin).get("results") else 1)'; then
+  echo "$report"
+  echo ">> SECRET gate FAILED: a credential was detected in the tree. See report above." >&2
+  status=1
+else
+  echo "no secrets detected."
+fi
+
+echo
+if [ "$status" -ne 0 ]; then
+  echo "SECURITY GATE: FAILED" >&2
+else
+  echo "SECURITY GATE: passed"
+fi
+exit "$status"