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/ux/navigation.md

@@ -0,0 +1,121 @@
+# Navigation Design
+
+## Goal
+
+Navigation should make the application structure obvious.
+
+---
+
+# Primary Navigation
+
+The application hierarchy:
+
+## Main
+
+Dashboard
+
+↓
+
+Jobs
+
+↓
+
+Applications
+
+↓
+
+Calendar / Follow-ups
+
+---
+
+## Career
+
+Career Profile
+
+↓
+
+CV Builder
+
+↓
+
+Cover Letters
+
+↓
+
+Portfolio
+
+---
+
+## Settings
+
+Account
+
+Connected Services
+
+AI Settings
+
+Preferences
+
+---
+
+# Sidebar Principles
+
+The sidebar should:
+
+- Be predictable.
+- Avoid excessive items.
+- Group related functionality.
+
+---
+
+# Current Direction
+
+Move Gmail/email settings into:
+
+Settings
+
+↓
+
+Connected Accounts
+
+---
+
+# Profile vs Career
+
+Important distinction:
+
+## Profile
+
+User account information:
+
+- Name.
+- Email.
+- Password.
+- Avatar.
+- Preferences.
+
+---
+
+## Career
+
+Professional identity:
+
+- Experience.
+- Skills.
+- CV.
+- Documents.
+
+Do not mix these.
+
+---
+
+# Mobile Navigation
+
+Mobile should prioritise:
+
+- Dashboard.
+- Jobs.
+- Add Job.
+- Career.
+
+Advanced settings can remain secondary.