Initial commit: SejeteralO water tarification platform

Full-stack app for participatory water pricing using Bezier curves.
- Backend: FastAPI + SQLAlchemy + SQLite with JWT auth
- Frontend: Nuxt 4 + TypeScript with interactive SVG editor
- Math engine: cubic Bezier tarification with Cardano solver
- Admin: commune management, household import, vote monitoring, CMS
- Citizen: interactive curve editor, vote submission
- Docker-compose deployment ready

Includes fixes for:
- Impact table snake_case/camelCase property mismatch
- CMS content backend API + frontend editor (was stub)
- Admin route protection middleware
- Public content display on commune page
- Vote confirmation page link fix

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

backend/app/engine/median.py

@@ -0,0 +1,48 @@
+"""
+Median computation for vote parameters.
+
+Computes the element-wise median of (vinf, a, b, c, d, e) across all active votes.
+This parametric median is chosen over geometric median because:
+- It's transparent and politically explainable
+- The result is itself a valid set of Bézier parameters
+"""
+
+import numpy as np
+from dataclasses import dataclass
+
+
+@dataclass
+class VoteParams:
+    """The 6 citizen-adjustable parameters."""
+    vinf: float
+    a: float
+    b: float
+    c: float
+    d: float
+    e: float
+
+
+def compute_median(votes: list[VoteParams]) -> VoteParams | None:
+    """
+    Compute element-wise median of vote parameters.
+
+    Returns None if no votes provided.
+    """
+    if not votes:
+        return None
+
+    vinfs = [v.vinf for v in votes]
+    a_s = [v.a for v in votes]
+    b_s = [v.b for v in votes]
+    c_s = [v.c for v in votes]
+    d_s = [v.d for v in votes]
+    e_s = [v.e for v in votes]
+
+    return VoteParams(
+        vinf=float(np.median(vinfs)),
+        a=float(np.median(a_s)),
+        b=float(np.median(b_s)),
+        c=float(np.median(c_s)),
+        d=float(np.median(d_s)),
+        e=float(np.median(e_s)),
+    )