feat(5.15+5.14): CLOSE — fix-uri code-review + embeddings functional

5.15 (propagare design + dashboard editare) si 5.14 (mapare LLM distilata)
inchise dupa /code-review high. 8 buguri reparate TDD:

- HIGH modal nu se deschidea pe randul slim (base.html: trimitere-slim)
- HIGH /repune trunchia prestatii (declaratie incompleta la RAR) -> iterare
  peste existing, codes pozitional
- HIGH embeddings incarca model ~230MB degeaba pe corpus gol -> poarta has_corpus()
- HIGH picker chips gol pe re-render eroare -> conn/account_id pe toate ramurile
- MED obs re-derivat dupa stergere explicita -> _merge_override pastreaza obs=''
- MED mapare salvata fara denumire poluă GOLD -> _record_gold_validation guard
- MED typo nome_prestatie -> nume_prestatie in select /repune
- MED bucketare timp +3h gresita iarna -> SQLite localtime + TZ=Europe/Bucharest

Embeddings WIRE-uit functional (PRD #15, decizie user): ensure_embeddings_corpus
construieste corpus din nomenclator, gated pe AUTOPASS_EMBEDDINGS_ENABLED (default
off). Marime model corectata ~50MB->~230MB (estimare PRD gresita).

Cleanup: hoist load_* din bucla bulk-fix; import re la top.
Regresie: 1256 passed, 1 deselected (live), 0 failed.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

app/api/v1/import_router.py

@@ -186,6 +186,14 @@ def _resolve_row_for_preview(
         denumire = str(denumire_val).strip() if denumire_val not in (None, "") else str(operatie_val)
         mapped["prestatii"] = [{"cod_op_service": str(operatie_val), "denumire": denumire}]
 
+    # obs derive-on-empty (D7/E3 PRD 5.15): daca obs e gol si avem operatie,
+    # copiem denumirea operatiei in obs (nu o mutam — op_service ramane neatins).
+    # DERIVE-ON-EMPTY: doar cand obs e gol, ca sa fie idempotent la re-preview/re-editare.
+    obs_curent = str(mapped.get("obs") or "").strip()
+    if not obs_curent and operatie_val:
+        obs_denumire = str(denumire_val).strip() if denumire_val not in (None, "") else str(operatie_val)
+        mapped["obs"] = obs_denumire
+
     # Canonicalizare: normalizeaza VIN/nr/odometru
     canon = canonicalize_row(mapped)
     mapped.update({
@@ -257,8 +265,9 @@ def _build_idempotency_key(account_id: int | None, resolved: dict[str, Any]) ->
 
 
 # Campuri de continut editabile in preview. Operatia/codul RAR NU se editeaza
-# aici (raman in panoul de mapare).
-EDIT_FIELDS = ("vin", "nr_inmatriculare", "data_prestatie", "odometru_initial", "odometru_final")
+# aici (raman in panoul de mapare). obs = text liber, se trateaza ca non-canonic
+# (doar .strip(), fara canonicalize_row) — urmeaza ramura `else` din _merge_override.
+EDIT_FIELDS = ("vin", "nr_inmatriculare", "data_prestatie", "odometru_initial", "odometru_final", "obs")
 
 
 def _merge_override(current: dict[str, Any], fields: dict[str, str | None]) -> dict[str, Any]:
@@ -279,7 +288,15 @@ def _merge_override(current: dict[str, Any], fields: dict[str, str | None]) -> d
             continue
         s = str(val).strip()
         if s == "":
-            out.pop(camp, None)  # empty = clear
+            if camp == "obs":
+                # obs e camp DERIVAT (copiaza denumirea operatiei cand e gol). Empty =
+                # STERGERE EXPLICITA a userului -> pastram obs='' in override ca
+                # derive-on-empty sa NU il re-deriveze (override aplicat ULTIMUL
+                # suprascrie derivarea, in preview si la commit). Un pop ar fi pierdut
+                # semnalul "sters explicit" -> obs re-derivat silentios din denumire.
+                out["obs"] = ""
+            else:
+                out.pop(camp, None)  # empty = clear (revine la valoarea din fisier)
         else:
             raw[camp] = s
     if raw:
@@ -1078,6 +1095,13 @@ def commit_import(
                     denumire = str(denumire_val).strip() if denumire_val not in (None, "") else str(operatie_val)
                     mapped["prestatii"] = [{"cod_op_service": str(operatie_val), "denumire": denumire}]
 
+                # obs derive-on-empty (D7/E3 PRD 5.15): copiere denumire in obs daca obs e gol.
+                # Identic cu logica din _resolve_row_for_preview (override aplicat tot ultimul).
+                obs_curent = str(mapped.get("obs") or "").strip()
+                if not obs_curent and operatie_val:
+                    obs_denumire = str(denumire_val).strip() if denumire_val not in (None, "") else str(operatie_val)
+                    mapped["obs"] = obs_denumire
+
                 # Rezolva prestatii INAINTE de canonicalizare (altfel cheia difera de cea din preview)
                 prestatii = mapped.get("prestatii") or []
                 resolved, _ = resolve_prestatii(prestatii, mapping, valid_codes, text_rules)
@@ -1180,12 +1204,14 @@ def commit_import(
 
 class RandEditIn(BaseModel):
     """Campuri de continut editabile in preview. None = ne-trimis (neschimbat);
-    "" = sterge override-ul (revine la valoarea din fisier)."""
+    "" = sterge override-ul (revine la valoarea din fisier).
+    obs = text liber fara validare de continut (US-005 PRD 5.15)."""
     vin: str | None = None
     nr_inmatriculare: str | None = None
     data_prestatie: str | None = None
     odometru_initial: str | None = None
     odometru_final: str | None = None
+    obs: str | None = None
 
 
 @router.post("/{import_id}/rand/{row_index}/editeaza")