feat: builder 简历生成 + 轻度优化 + 简历导入交付副本

自内部仓库剥离深度优化与 RAG 知识库后的交付版本：
- Builder 对话式简历生成（FSM + 意图路由 LLM 兜底增强）
- 条目级轻度优化：事实覆盖门禁 + STAR/bullet 修复链，功能/简介/成果与技术栈同级保护
- 简历导入：DOCX/PDF 解析、结构归一、手机号脱敏
- PostgreSQL 运行时 + Alembic 迁移链

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

backend/app/optimization_tiers.py

@@ -0,0 +1,55 @@
+"""Membership-tier parameters for the shared optimization pipeline."""
+
+from __future__ import annotations
+
+import os
+from dataclasses import dataclass
+from typing import Any
+
+
+@dataclass(frozen=True, slots=True)
+class TierConfig:
+    tier: str
+    deep_allowed: bool
+    max_questions: int
+    min_questions: int
+    gap_threshold: float
+    include_gap_report: bool
+
+
+TIER_CONFIGS: dict[str, TierConfig] = {
+    "free": TierConfig(
+        tier="free",
+        deep_allowed=False,
+        max_questions=0,
+        min_questions=0,
+        gap_threshold=5.0,
+        include_gap_report=True,
+    ),
+    "vip": TierConfig(
+        tier="vip",
+        deep_allowed=True,
+        max_questions=6,
+        min_questions=2,
+        gap_threshold=8.0,
+        include_gap_report=True,
+    ),
+}
+
+
+def tier_config_for_session(session: dict[str, Any]) -> TierConfig:
+    """Resolve an explicit entitlement first, then the local development default."""
+    raw = str(
+        (session.get("profile") or {}).get("entitlement_tier") or _default_tier()
+    ).strip().lower()
+    return TIER_CONFIGS.get(raw, TIER_CONFIGS["free"])
+
+
+def _default_tier() -> str:
+    """Use a local-only default tier when RESUME_AGENT_DEFAULT_TIER is configured.
+
+    Explicit session entitlements always take precedence. Production deployments must
+    leave this environment variable unset so the default remains ``free``.
+    """
+    value = os.environ.get("RESUME_AGENT_DEFAULT_TIER", "free").strip().lower()
+    return value if value in TIER_CONFIGS else "free"