feat(script): one-time fix_existing personas' openers to natural Thai

Deterministic, conservative: only rewrites openers that lead with a casual
interjection (เฮ้/เอ้/เอ่อ/เอ๊ะ/อืม/เออ/นี่ๆ/ว่าไง/hey/hi/hiya/yo) or a bare
politeness word (ครับ/ค่ะ). Leaves natural Thai and English openers untouched.
Prints before -> after. Run in the container console:
  cd /app/backend && python3 scripts/fix_openers.py

backend/scripts/fix_openers.py

@@ -0,0 +1,86 @@
+"""One-time data fix (run in the EasyPanel container console):
+Rewrite existing personas' openers (opener) to natural Thai.
+
+Only rewords openers that OPEN with a casual interjection/filler
+(เฮ้ / เอ้ / เอ่อ / เอ๊ะ / อืม / เออ / นี่ๆ / ว่าไง / hey / hi / hiya / yo ...).
+Everyone else is left untouched (safe & reversible). Prints before -> after.
+
+Usage:
+  cd /app/backend
+  python3 /path/to/fix_openers.py        # or paste as a heredoc
+"""
+from __future__ import annotations
+
+import re
+from pathlib import Path
+
+from app.config import Config
+from app.services.groups import GroupStore
+
+# Leading casual interjections/filler that make a Thai opener sound unnatural.
+FILLER = re.compile(
+    r"^(?:เฮ้|เอ้|เอ่อ|เอ๊ะ|อืม|เออ|นี่ๆ|นี่|ว่าไง|เฮย์|hey|hiya|hi|hello|yo)"
+    r"[\s:,\-–—]*",
+    re.IGNORECASE,
+)
+BARE_POLITE = re.compile(r"^(ครับ|ค่ะ)(\s|$)")
+THAI_CHAR = re.compile(r"[\u0E00-\u0E7F]")
+
+
+def fix_opener(existing: str) -> str | None:
+    """Return the rewritten opener, or None when nothing needs changing."""
+    if not isinstance(existing, str) or not existing.strip():
+        return None
+    s = existing.strip()
+    # Only target Thai openers; leave English ones untouched.
+    if not THAI_CHAR.search(s):
+        return None
+
+    # 1) Strip leading casual fillers (เฮ้ / เอ้ / เอ่อ / hey / hi / ...).
+    m = FILLER.match(s)
+    grand_rest = s[m.end():].strip(" ,-–—:;") if m else s.strip()
+    new = grand_rest
+
+    # 2) If it now (or originally) opens with a bare politeness word, prepend
+    #    the proper greeting: "ครับ สนใจ..."  ->  "สวัสดีครับ สนใจ..."
+    bp = BARE_POLITE.match(new)
+    if bp:
+        polite = new[: len(bp.group(1))]
+        new = new[len(polite):].strip(" ,-–—:;") or ""
+        new = "สวัสดี" + polite + ((" " + new) if new else "")
+
+    cleaned = " ".join(new.split())
+    if not cleaned or cleaned == s:
+        return None  # nothing meaningful changed (or was empty)
+    return cleaned[:400]
+
+
+def main() -> None:
+    store = GroupStore(Config.DATA_DIR)
+    groups = store.groups.all()
+    fixed = skipped = 0
+    seen: set[str] = set()
+    for group in groups:
+        gid = group.get("id") or group.get("_id")
+        if not gid or gid in seen:
+            continue
+        seen.add(gid)
+        raw = group.get("personas") or []
+        personas = [p for p in raw if isinstance(p, dict) and p.get("id")]
+        for p in personas:
+            oid = p.get("id")
+            old = p.get("opener") or ""
+            new = fix_opener(old)
+            if new is None:
+                skipped += 1
+                continue
+            print(f"[{gid}] persona={oid!r}")
+            print(f"   before: {old!r}")
+            print(f"   after : {new!r}")
+            store.update_persona(gid, oid, {"opener": new})
+            fixed += 1
+    print(f"\nDONE — fixed: {fixed}, left-as-is: {skipped}")
+
+
+if __name__ == "__main__":
+    main()