Fix disabled Passage routes failing with 500

[kingpy-bot]

Fixes #97.

What changed

• keep PassageServiceInterface container-resolvable when the master switch is off
• return a fail-closed 404 before resolving the route handler or making any upstream request
• add regression coverage for both disabled boot binding and disabled-route behavior

This preserves registered route definitions while making PASSAGE_ENABLED=false safely disable all proxying instead of failing during controller construction.

Verification

• vendor/bin/pest: 105 tests passed, 263 assertions
• vendor/bin/pint --test on all four touched files: passed
• git diff --check: passed

AI-assisted implementation and verification.