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/_archive/claude.md

@@ -0,0 +1,20 @@
+# Jobjakt Development Context
+
+Before making changes:
+
+1. Read docs/00-ai-context.md
+2. Read relevant feature documentation
+3. Check existing implementation
+4. Prefer incremental changes
+
+The application is a job tracking platform.
+
+The CV builder is a supporting Career Workspace feature.
+
+Never redesign Jobjakt into only a CV builder.
+
+Existing working functionality must be preserved.
+
+When uncertain:
+- Ask for clarification.
+- Do not make large assumptions.