[AZ-263] Bootstrap: repo skeleton + Docker + CI + Alembic + Tier-1 tests

Implements the AZ-263 / E-BOOT initial structure task:

- Python src/-layout package `gps_denied_onboard/` with per-component
  interface stubs (14 components), type-only DTOs under `_types/`,
  shared helpers under `helpers/` (R14 LightGlue ownership), structured
  JSON logging, runtime composition root with env-var fail-fast gate,
  healthcheck module shared by Docker and CI smoke.
- CMake top-level + `cmake/{build_options,dependencies,strategies}.cmake`
  with the BUILD_* per-binary flags (ADR-002) and pinned external git
  refs for OKVIS2 / VINS-Mono / GTSAM / FAISS / OpenCV >=4.12.0.
- Three Dockerfiles (companion-tier1, operator-tooling,
  mock-suite-sat-service) + two compose files (dev + Tier-1 test).
- Four GitHub Actions workflows: ci.yml (lint/unit/integration/dual
  binary build/SBOM diff/security), ci-tier2.yml (self-hosted Jetson
  AC-bound NFTs), release.yml, cve-rescan.yml.
- Two CI gate scripts: `ci/sbom_diff.py` (deployment SBOM subset +
  R02 exclusion), `ci/opencv_pin_gate.py` (>=4.12.0 enforcement,
  D-CROSS-CVE-1).
- Alembic-driven Postgres 16 initial migration `0001_initial.py`
  mirroring satellite-provider tiles + flights + sector_classifications
  + manifests + engine_cache_entries (data_model.md s 2).
- Tier-1 test scaffolding: 95 passing unit tests covering every AC,
  per-component smoke tests, structured logging JSON output check,
  env-var gate check, healthcheck import check. Two CI-gated tests
  (cmake configure, actionlint) skip locally with explicit reasons.
- Batch report + code review report under `_docs/03_implementation/`.

Verdict: PASS_WITH_WARNINGS (two Low findings, both informational).
Co-authored-by: Cursor <cursoragent@cursor.com>

db/migrations/script.py.mako

@@ -0,0 +1,26 @@
+"""${message}
+
+Revision ID: ${up_revision}
+Revises: ${down_revision | comma,n}
+Create Date: ${create_date}
+"""
+from __future__ import annotations
+
+from typing import Sequence, Union
+
+from alembic import op
+import sqlalchemy as sa
+${imports if imports else ""}
+
+revision: str = ${repr(up_revision)}
+down_revision: Union[str, None] = ${repr(down_revision)}
+branch_labels: Union[str, Sequence[str], None] = ${repr(branch_labels)}
+depends_on: Union[str, Sequence[str], None] = ${repr(depends_on)}
+
+
+def upgrade() -> None:
+    ${upgrades if upgrades else "pass"}
+
+
+def downgrade() -> None:
+    ${downgrades if downgrades else "pass"}