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/security/user-data.md

@@ -0,0 +1,48 @@
+# User Data Protection
+
+## Purpose
+
+Protect personal career information.
+
+---
+
+# Stored Data
+
+Potential sensitive information:
+
+- CV content.
+- Employment history.
+- Contact information.
+- Documents.
+- Email communication.
+
+---
+
+# Requirements
+
+Support:
+
+- User export.
+- User deletion.
+- Data ownership.
+
+---
+
+# Database
+
+Ensure:
+
+- Correct relationships.
+- No cross-user queries.
+- Safe migrations.
+
+---
+
+# Logging
+
+Never log:
+
+- Passwords.
+- Tokens.
+- Private documents.
+- Sensitive CV content.