feat: add backup CLI commands, AI correction/modifier services, and timezone-aware date display

- Add `devplace backups` CLI subcommands (list, run, prune, clear) with job enqueueing and orphan cleanup
- Introduce `BACKUPS_DIR` and `BACKUP_STAGING_DIR` config paths for backup storage
- Implement `schedule_correction` and `schedule_modification` calls in content creation, comment creation, and comment editing flows
- Add `DEFAULT_CORRECTION_PROMPT` and `DEFAULT_MODIFIER_PROMPT` config constants for AI content processing
- Document timezone-aware date display using `local_dt`/`dt_ago` Jinja globals with client-side `Intl` localization
- Update README with AI content correction/modifier support in direct messages via `@ai` inline instructions
- Add `track_action(user["uid"], "vote")` call on upvote in `apply_vote`

devplacepy/routers/profile/usage.py

@@ -2,12 +2,40 @@
 
 import logging
 
+from devplacepy.database import get_correction_usage, get_modifier_usage
 from devplacepy.services.manager import service_manager
 from devplacepy.services.openai_gateway.analytics import user_spend_24h
 
 logger = logging.getLogger(__name__)
 
 
+def _usage_view(data: dict, include_cost: bool) -> dict:
+    usage = {
+        "calls": data["calls"],
+        "prompt_tokens": data["prompt_tokens"],
+        "completion_tokens": data["completion_tokens"],
+        "total_tokens": data["total_tokens"],
+        "avg_tokens": data["avg_tokens"],
+        "avg_latency_ms": data["avg_upstream_latency_ms"],
+        "avg_total_latency_ms": data["avg_total_latency_ms"],
+        "avg_tokens_per_second": data["avg_tokens_per_second"],
+        "total_time_s": round(data["upstream_latency_ms"] / 1000.0, 1),
+        "last_used": data["updated_at"],
+    }
+    if include_cost:
+        usage["cost_usd"] = round(data["cost_usd"], 6)
+        usage["avg_cost_usd"] = round(data["avg_cost_usd"], 6)
+    return usage
+
+
+def _correction_usage(user_uid: str, include_cost: bool = False) -> dict:
+    return _usage_view(get_correction_usage(user_uid), include_cost)
+
+
+def _modifier_usage(user_uid: str, include_cost: bool = False) -> dict:
+    return _usage_view(get_modifier_usage(user_uid), include_cost)
+
+
 def _ai_quota(
     user_uid: str, include_cost: bool = False, is_admin: bool = False
 ) -> dict | None: