feat(prospecting): implement security audit pipeline (Workstream 2A)

Complete security audit integration into the enrichment pipeline:

Backend:
- SecurityAuditService with 7 passive checks: HTTPS, SSL cert, security
  headers, exposed files, cookies, server info, technology detection
- Constants file with SECURITY_HEADERS, EXPOSED_PATHS, SEVERITY_SCORES
- SecurityAuditResponse schema with JSON field validators + aliases
- Endpoints: POST /security-audit/{id}, POST /security-audit/batch
- Added to full_enrichment pipeline (Step 5, before scoring)
- get_pending_security_audit() query in prospect_service

Frontend:
- Security tab on prospect detail page with grade badge (A+ to F),
  score/100, severity counts, HTTPS/SSL status, missing headers,
  exposed files, technologies, and full findings list
- "Run Security Audit" button with loading state
- "Security Audit" batch button on scan-jobs page

Tested on batirenovation-strasbourg.fr: Grade D (50/100), 11 issues
found (missing headers, exposed wp-login, server version disclosure).

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

app/modules/prospecting/schemas/security_audit.py

@@ -0,0 +1,82 @@
+# app/modules/prospecting/schemas/security_audit.py
+"""Pydantic schemas for security audit responses."""
+
+import json
+from datetime import datetime
+
+from pydantic import BaseModel, Field, field_validator
+
+
+class SecurityAuditFinding(BaseModel):
+    """A single security finding."""
+
+    title: str
+    severity: str
+    category: str
+    detail: str
+    is_positive: bool = False
+
+
+class SecurityAuditResponse(BaseModel):
+    """Schema for security audit detail response."""
+
+    id: int
+    prospect_id: int
+    score: int
+    grade: str
+    detected_language: str | None = None
+    findings: list[SecurityAuditFinding] = Field(default=[], validation_alias="findings_json")
+    findings_count_critical: int = 0
+    findings_count_high: int = 0
+    findings_count_medium: int = 0
+    findings_count_low: int = 0
+    findings_count_info: int = 0
+    has_https: bool | None = None
+    has_valid_ssl: bool | None = None
+    ssl_expires_at: datetime | None = None
+    missing_headers: list[str] = Field(default=[], validation_alias="missing_headers_json")
+    exposed_files: list[str] = Field(default=[], validation_alias="exposed_files_json")
+    technologies: list[str] = Field(default=[], validation_alias="technologies_json")
+    scan_error: str | None = None
+    created_at: datetime
+    updated_at: datetime
+
+    @field_validator("findings", mode="before")
+    @classmethod
+    def parse_findings(cls, v):
+        if isinstance(v, str):
+            return json.loads(v)
+        return v
+
+    @field_validator("missing_headers", mode="before")
+    @classmethod
+    def parse_missing_headers(cls, v):
+        if isinstance(v, str):
+            return json.loads(v)
+        return v or []
+
+    @field_validator("exposed_files", mode="before")
+    @classmethod
+    def parse_exposed_files(cls, v):
+        if isinstance(v, str):
+            return json.loads(v)
+        return v or []
+
+    @field_validator("technologies", mode="before")
+    @classmethod
+    def parse_technologies(cls, v):
+        if isinstance(v, str):
+            return json.loads(v)
+        return v or []
+
+    class Config:
+        from_attributes = True
+
+
+class SecurityAuditSingleResponse(BaseModel):
+    """Response for single-prospect security audit."""
+
+    domain: str
+    score: int
+    grade: str
+    findings_count: int