docs: reorganize tree, restore architecture + research from archive, add Phase 0 reports

Active docs/ was stub scaffolding while the real docs sat in docs/_archive/.
Restore and correct them, and record the Phase 0 work.

- docs/architecture/current.md: verified system map (from archived SYSTEM_OVERVIEW,
  9 corrections against code).
- docs/research/competitors.md: sourced competitor analysis (from archived
  PRODUCT_RESEARCH, feature matrix corrected).
- docs/decisions/ADR-002-job-application-model.md: the Job/JobApplication split.
- docs/application-discovery-report.md, docs/implementation-roadmap.md,
  docs/phase-0-foundation-report.md, docs/career-workspace-branch-assessment.md.
- Remove 10 zero-byte placeholder files that advertised content that never existed.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

docs/technical/testing.md

@@ -0,0 +1,65 @@
+# Testing Strategy
+
+## Goal
+
+Maintain confidence while changing the application.
+
+---
+
+# Test Areas
+
+## Backend
+
+Test:
+
+- Business logic.
+- Services.
+- APIs.
+- Database behaviour.
+
+---
+
+## Frontend
+
+Test:
+
+- Important workflows.
+- Components.
+- User interactions.
+
+---
+
+# Priority Workflows
+
+Must protect:
+
+## Authentication
+
+- Signup.
+- Login.
+- OAuth.
+- Password reset.
+- 2FA.
+
+---
+
+## Jobs
+
+- Creating jobs.
+- Updating status.
+- Follow-ups.
+
+---
+
+## Career
+
+- CV upload.
+- CV extraction.
+- CV generation.
+- PDF generation.
+
+---
+
+# Production Confidence
+
+Critical user journeys should have automated tests.