Switch telemetry to proxy_telemetry_v2 table, bump to 0.5.12

Telemetry beacon now writes to proxy_telemetry_v2 which has all 25
columns matching the beacon payload. Added SQL schema for the new table.

sql/create_proxy_telemetry_v2.sql

@@ -0,0 +1,70 @@
+-- Supabase SQL: Create proxy_telemetry_v2 table
+-- Run this in the Supabase SQL Editor (https://supabase.com/dashboard → SQL Editor)
+-- This table matches every field the beacon code writes in headroom/telemetry/beacon.py
+
+CREATE TABLE IF NOT EXISTS proxy_telemetry_v2 (
+    id uuid DEFAULT gen_random_uuid() PRIMARY KEY,
+    created_at timestamptz DEFAULT now() NOT NULL,
+
+    -- Core identity (always present)
+    session_id text NOT NULL,
+    instance_id text,
+    headroom_version text,
+    python_version text,
+    os text,
+    sdk text,
+    backend text,
+    session_minutes integer,
+
+    -- Effectiveness metrics
+    tokens_saved bigint,
+    requests integer,
+    compression_percent real,
+    cache_hit_rate real,
+    cost_saved_usd real,
+    cache_saved_usd real,
+    models_used jsonb,
+
+    -- Performance overhead
+    overhead_avg_ms real,
+    overhead_max_ms real,
+
+    -- TTFB
+    ttfb_avg_ms real,
+
+    -- Pipeline timing (JSONB: {transform_name: avg_ms})
+    pipeline_timing jsonb,
+
+    -- Request patterns
+    avg_tokens_before integer,
+    avg_tokens_after integer,
+
+    -- Compression cache
+    compression_cache jsonb,
+
+    -- CCR usage
+    ccr jsonb,
+
+    -- Waste signals
+    waste_signals jsonb
+);
+
+-- Index for querying by session and time
+CREATE INDEX IF NOT EXISTS idx_ptv2_session_id ON proxy_telemetry_v2(session_id);
+CREATE INDEX IF NOT EXISTS idx_ptv2_created_at ON proxy_telemetry_v2(created_at DESC);
+CREATE INDEX IF NOT EXISTS idx_ptv2_version ON proxy_telemetry_v2(headroom_version);
+
+-- Enable Row Level Security
+ALTER TABLE proxy_telemetry_v2 ENABLE ROW LEVEL SECURITY;
+
+-- RLS policies: anon can INSERT (telemetry beacon) and SELECT (for debugging)
+CREATE POLICY "anon_insert" ON proxy_telemetry_v2
+    FOR INSERT TO anon
+    WITH CHECK (true);
+
+CREATE POLICY "anon_select" ON proxy_telemetry_v2
+    FOR SELECT TO anon
+    USING (true);
+
+-- Grant permissions to anon role
+GRANT INSERT, SELECT ON proxy_telemetry_v2 TO anon;