fix: allow edge-contact copper for off-board components

[KrishnaX12]

Summary

Fixes #228 by skipping the copper-to-board-edge clearance check for copper elements (SMT pads and plated holes) belonging to components marked allowOffBoard (is_allowed_to_be_off_board: true).

Problem

An SMT pad or component intentionally placed at or over the board boundary (such as an edge contact / finger jumper) was reported as violating the copper-to-board-edge clearance rule because checkCopperToBoardEdgeClearance did not check is_allowed_to_be_off_board on the owning pcb_component.

Solution

1. In lib/check-copper-to-board-edge-clearance.ts, collect component IDs with is_allowed_to_be_off_board === true.
2. Skip copper elements (pcb_smtpad, pcb_plated_hole) whose pcb_component_id matches an allowed off-board component.
3. Update tests/repros/repro-edge-contact-pad-clearance.test.tsx from test.failing to test with an inline snapshot assertion expect(errors).toMatchInlineSnapshot("[]").

Verification

• bun test tests/repros/repro-edge-contact-pad-clearance.test.tsx passes
• bun test passes (183 pass, 0 fail across 81 files)
• bun run format and bun run build pass cleanly

[KrishnaX12]

Visual & Snapshot Verification

• Diagnostic Output: checkCopperToBoardEdgeClearance now returns [] (0 errors) when allowOffBoard is set on the component. Added inline snapshot expect(errors).toMatchInlineSnapshot("[]").
• Board Geometry: The $2\text{mm} \times 7\text{mm}$ SMT pad is placed $0.01\text{mm}$ from the bottom board edge outline.
• Test Suite: All 183 tests pass cleanly.