Add pensions module and integrate with tax report

Adds a full pensions feature: SIPP/workplace DC/LISA account metadata,
contribution recording with relief-at-source/net-pay/salary-sacrifice
gross calculations, state pension tracker, annual allowance monitor,
and LISA summary. Pension contributions feed into the tax report
(RAS gross totals, allowance used). Includes two Alembic migrations,
backend service/schema/API, and full frontend pensions page with
cards for allowance, state pension, LISA, and retirement projection.

Also fixes CSRF cookie secure flag (must be false for HTTP deployments)
and extends tax schemas/service to expose pension data in the report.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/app/schemas/tax.py

@@ -203,6 +203,17 @@ class IncomeSummary(BaseModel):
     payslips: list[dict[str, Any]]
 
 
+class PensionTaxSummary(BaseModel):
+    net_pay_total: str
+    salary_sacrifice_total: str
+    ras_gross_total: str
+    higher_rate_claimable: str
+    additional_rate_claimable: str
+    annual_allowance_used: str
+    annual_allowance_remaining: str
+    standard_allowance: str
+
+
 class TaxReportResponse(BaseModel):
     tax_year: int
     tax_year_display: str
@@ -212,4 +223,5 @@ class TaxReportResponse(BaseModel):
     ni: NISummary
     cgt: CGTSummary
     dividends: DividendSummary
+    pensions: PensionTaxSummary | None
     summary: TaxReportSummary