docs: add standardized comments to all services (Python, Go, Bash)

- Add docs/commenting-standard.md defining per-language comment standards
  (Go godoc, Python PEP-257, C Doxygen, Bash header blocks, SQL banners)

- services/dashboard: 100% docstring coverage (100/100 functions)
  - All FastAPI route handlers, helpers, classes, and models documented
  - Language: French (project convention)

- services/bot-detector: 100% docstring coverage (53/53 symbols)
  - bot_detector.py: 14 functions + module docstring
  - anubis/fetch_rules.py: 9 functions

- shared/python/ja4_common: full docstrings on ClickHouseClient (7 methods)
  and ClickHouseSettings class

- services/correlator: 24 godoc comments added across 6 Go files
  - correlation_service.go: 10 private helpers
  - unixsocket/source.go: 6 parsing/socket helpers
  - correlated_log.go: 4 field extraction helpers
  - orchestrator.go, logger.go, main.go: 4 comments

- services/correlator/scripts/audit-architecture.sh: standardized header block

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

services/dashboard/backend/routes/metrics.py

@@ -144,6 +144,7 @@ async def get_metrics_baseline():
         row = r.result_rows[0] if r.result_rows else None
 
         def pct_change(today: int, yesterday: int) -> float:
+            """Calcule la variation en pourcentage entre aujourd'hui et hier. Retourne 100 si hier=0 et aujourd'hui>0."""
             if yesterday == 0:
                 return 100.0 if today > 0 else 0.0
             return round((today - yesterday) / yesterday * 100, 1)