feat: add metrics services and aggregation engine

New modules:
- spp_metrics_services: demographic dimensions and shared metric computation
  services built on CEL domain
- spp_aggregation: unified aggregation engine with TTL-based caching,
  scope-based access control, and cron-managed cache cleanup

Author: jeremi

spp_aggregation/__init__.py

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+# Part of OpenSPP. See LICENSE file for full copyright and licensing details.
+
+from . import models

spp_aggregation/__manifest__.py

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+# Part of OpenSPP. See LICENSE file for full copyright and licensing details.
+{
+    "name": "OpenSPP Aggregation Engine",
+    "summary": "Unified aggregation service for statistics, simulations, and GIS queries",
+    "category": "OpenSPP",
+    "version": "19.0.2.0.0",
+    "sequence": 1,
+    "author": "OpenSPP.org",
+    "website": "https://github.com/OpenSPP/OpenSPP2",
+    "license": "LGPL-3",
+    "development_status": "Alpha",
+    "maintainers": ["jeremi"],
+    "depends": [
+        "base",
+        "spp_cel_domain",
+        "spp_area",
+        "spp_registry",
+        "spp_security",
+        "spp_metrics_services",
+    ],
+    "data": [
+        # Security
+        "security/aggregation_security.xml",
+        "security/ir.model.access.csv",
+        # Data
+        "data/cron_cache_cleanup.xml",
+        # Views
+        "views/aggregation_scope_views.xml",
+        "views/aggregation_access_views.xml",
+        "views/menu.xml",
+    ],
+    "assets": {},
+    "demo": [],
+    "images": [],
+    "application": False,
+    "installable": True,
+    "auto_install": False,
+    "description": """
+OpenSPP Aggregation Engine
+==========================
+
+Provides a centralized aggregation service that unifies statistics computation
+across simulation, GIS API, and dashboards.
+
+Features
+--------
+
+- **Unified Scopes**: Define targeting with CEL expressions, spatial polygons,
+  administrative areas, or explicit IDs
+- **Multi-dimensional Breakdown**: Group by configurable demographic dimensions
+  (gender, disability, area, age group)
+- **Privacy Protection**: K-anonymity with complementary suppression prevents
+  differencing attacks
+- **Access Control**: Aggregate-only access for researchers (no individual records)
+- **Distribution Statistics**: Gini coefficient, Lorenz curve, percentiles
+- **Fairness Analysis**: Parity analysis across demographic groups
+
+Architecture
+------------
+
+::
+
+    ┌─────────────────────────────────────────────────────────┐
+    │                      CONSUMERS                           │
+    ├─────────────┬─────────────┬─────────────┬───────────────┤
+    │ Simulation  │   GIS API   │ QGIS Plugin │  Dashboards   │
+    └──────┬──────┴──────┬──────┴──────┬──────┴───────┬───────┘
+           │             │             │              │
+           ▼             ▼             ▼              ▼
+    ┌─────────────────────────────────────────────────────────┐
+    │          spp.aggregation.service (AbstractModel)         │
+    │                                                          │
+    │  compute_aggregation(scope, statistics, group_by)        │
+    └─────────────────────────────────────────────────────────┘
+
+Models
+------
+
+- ``spp.aggregation.scope``: Unified targeting scope (CEL, spatial, area)
+- ``spp.aggregation.access.rule``: Access control for aggregate-only users
+- ``spp.demographic.dimension``: Configurable breakdown dimensions
+
+Services
+--------
+
+- ``spp.aggregation.service``: Main computation entry point
+- ``spp.aggregation.scope.resolver``: Resolve scope to registrant IDs
+- ``spp.aggregation.cache``: TTL-based result caching
+- ``spp.metrics.distribution``: Gini, Lorenz, percentiles
+- ``spp.metrics.fairness``: Parity analysis
+- ``spp.metrics.privacy``: K-anonymity enforcement
+    """,
+}

spp_aggregation/data/cron_cache_cleanup.xml

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+<?xml version="1.0" encoding="utf-8"?>
+<odoo>
+    <data noupdate="1">
+        <!-- Cron job to clean up expired cache entries -->
+        <record id="ir_cron_cache_cleanup" model="ir.cron">
+            <field name="name">Aggregation: Cache Cleanup</field>
+            <field name="model_id" ref="model_spp_aggregation_cache_entry"/>
+            <field name="state">code</field>
+            <field name="code">model.cron_cleanup_expired()</field>
+            <field name="interval_number">1</field>
+            <field name="interval_type">hours</field>
+            <field name="active">True</field>
+        </record>
+    </data>
+</odoo>

spp_aggregation/models/__init__.py

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+# Part of OpenSPP. See LICENSE file for full copyright and licensing details.
+
+from . import aggregation_scope
+from . import aggregation_access
+from . import service_scope_resolver
+from . import service_cache
+from . import statistic_registry
+from . import service_aggregation