refactor(server): 单号规则收紧为 A/R/D+8 位紧凑格式

- DOCUMENT_NUMBER_PREFIXES 改为 A/R/D，新增短格式与旧格式正则并存识别，提取正则加边界锚定避免误匹配
- build_document_number 去掉时间戳段，统一生成 A+token 等紧凑单号，is_application_claim_no 兼容旧 AP-/APP- 前缀
- access_policy/status_registry/reimbursements/expense_claims/budget_support 统一复用 is_application_claim_no 判定申请单
- 同步 document_numbering 单元测试覆盖新旧两种格式

server/src/app/services/budget_support.py

@@ -23,6 +23,7 @@ from app.services.budget_types import (
     SUBJECT_CODE_ALIASES,
     SUPPORTED_BUDGET_SUBJECT_CODES,
 )
+from app.services.document_numbering import is_application_claim_no
 from app.services.expense_claim_constants import EXPENSE_TYPE_LABELS
 from app.services.expense_claim_risk_stage import enrich_risk_flag_semantics
 from app.services.expense_type_keywords import resolve_expense_type_code_from_text
@@ -349,7 +350,11 @@ class BudgetSupportMixin:
     def _reservation_source_type_from_claim(claim: ExpenseClaim) -> str:
         claim_no = str(claim.claim_no or "").strip().upper()
         expense_type = str(claim.expense_type or "").strip().lower()
-        if claim_no.startswith(("AP-", "APP-")) or expense_type == "application" or expense_type.endswith("_application"):
+        if (
+            is_application_claim_no(claim_no)
+            or expense_type == "application"
+            or expense_type.endswith("_application")
+        ):
             return "application"
         return "claim"