feat: Replace SQLite with per-user JSON storage (fixes #2)

- Add storage.py with load_user(), save_user(), next_bounty_id()
- Rewrite commands.py to use JSON storage (simplified)
- Remove db.py, schema.sql, cron.py, test_db.py
- Update SPEC.md to reflect new architecture
- Admin model removed (anyone can add, creator only can edit/delete)
- No reminders in v1

apps/telegram-bot/storage.py

@@ -0,0 +1,49 @@
+"""Per-user JSON file storage for JIGAIDO."""
+
+import json
+import tempfile
+import os
+from pathlib import Path
+from typing import Optional
+
+DATA_DIR = Path(__file__).parent / "data"
+USERS_DIR = DATA_DIR / "users"
+
+
+def _ensure_dirs() -> None:
+    USERS_DIR.mkdir(parents=True, exist_ok=True)
+
+
+def _user_file_path(telegram_user_id: int) -> Path:
+    return USERS_DIR / f"{telegram_user_id}.json"
+
+
+def load_user(telegram_user_id: int) -> dict:
+    """Load user data from JSON file. Returns empty user structure if not found."""
+    _ensure_dirs()
+    path = _user_file_path(telegram_user_id)
+    if not path.exists():
+        return {
+            "user_id": telegram_user_id,
+            "username": None,
+            "personal_bounties": [],
+            "tracked_bounties": [],
+        }
+    with open(path) as f:
+        return json.load(f)
+
+
+def save_user(user_data: dict) -> None:
+    """Atomically save user data to JSON file."""
+    _ensure_dirs()
+    path = _user_file_path(user_data["user_id"])
+    with tempfile.NamedTemporaryFile(mode="w", dir=USERS_DIR, delete=False) as tmp:
+        json.dump(user_data, tmp, indent=2)
+        tmp_path = tmp.name
+    os.rename(tmp_path, path)
+
+
+def next_bounty_id(user_data: dict) -> int:
+    """Get next sequential bounty ID for user's file."""
+    existing_ids = [b["id"] for b in user_data.get("personal_bounties", [])]
+    return (max(existing_ids) + 1) if existing_ids else 1