feat(mapari): regula 'exclude de la declarare' per operatie + stare preview Nedeclarat

Operatiile care nu se declara la RAR (ex. ITP facturat in service) primesc o
regula exclus=1 in operations_mapping, setabila din panoul de mapare al
preview-ului de import si din tab-ul Mapari (optiunea 'Nu se declara la RAR').

- resolve_prestatii(excluded_ops): item nemapat cu op exclusa -> adnotat exclus,
  nu mai e needs_mapping; precedenta: cod explicit > exclus > mapare > reguli text
- split_prestatii_excluse: itemii exclusi nu intra niciodata in payload/cheie
- preview import: rand cu toate operatiile excluse -> stare 'excluded'
  (eticheta Nedeclarat), necomis; operatia dispare din panoul de mapat
- reresolve/corectie/API: submission cu toate operatiile excluse -> needs_data
  cu motiv explicit; ingestia API trateaza excluderea la clasificare
- migrare: coloana operations_mapping.exclus + rebuild import_rows pentru
  CHECK-ul resolved_status cu 'excluded' (o singura data, gardat pe sqlite_master)
- fix flake: clamp similaritate embeddings la [-1,1] (float32 dadea 1.0000001)

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

app/schema.sql

@@ -82,8 +82,9 @@ CREATE TABLE IF NOT EXISTS operations_mapping (
     id              INTEGER PRIMARY KEY AUTOINCREMENT,
     account_id      INTEGER NOT NULL REFERENCES accounts(id) ON DELETE CASCADE,
     cod_op_service  TEXT NOT NULL,
-    cod_prestatie   TEXT NOT NULL,
+    cod_prestatie   TEXT NOT NULL,          -- gol ('') cand exclus=1 (regula nu mapeaza)
     auto_send       INTEGER NOT NULL DEFAULT 1,
+    exclus          INTEGER NOT NULL DEFAULT 0, -- 1 = operatia NU se declara la RAR
     created_at      TEXT NOT NULL DEFAULT (datetime('now')),
     UNIQUE (account_id, cod_op_service)
 );
@@ -175,7 +176,8 @@ CREATE TABLE IF NOT EXISTS import_rows (
     resolved_status TEXT NOT NULL DEFAULT 'pending'
                         CHECK (resolved_status IN (
                             'pending','ok','needs_mapping','needs_data',
-                            'needs_review','already_sent','duplicate_in_file'
+                            'needs_review','already_sent','duplicate_in_file',
+                            'excluded'
                         )),
     error           TEXT
 );