v0.1.17: UI fixes, Linux improvements, documentation overhaul

UI/UX:
- Fix heartbeat auto-refresh and rate-limiting page
- Add navigation breadcrumbs to settings pages
- New screenshots added

Linux Agent v0.1.17:
- Fix disk detection for multiple mount points
- Improve installer idempotency
- Prevent duplicate registrations

Documentation:
- README rewrite: 538→229 lines, homelab-focused
- Split docs: API.md, CONFIGURATION.md, DEVELOPMENT.md
- Add NOTICE for Apache 2.0 attribution

aggregator-server/internal/database/migrations/012_add_token_seats.up.sql

@@ -0,0 +1,118 @@
+-- Add seat tracking to registration tokens for multi-use support
+-- This allows tokens to be used multiple times up to a configured limit
+
+-- Add seats columns
+ALTER TABLE registration_tokens
+    ADD COLUMN max_seats INT NOT NULL DEFAULT 1,
+    ADD COLUMN seats_used INT NOT NULL DEFAULT 0;
+
+-- Backfill existing tokens
+-- Tokens with status='used' should have seats_used=1, max_seats=1
+UPDATE registration_tokens
+SET seats_used = 1,
+    max_seats = 1
+WHERE status = 'used';
+
+-- Active/expired/revoked tokens get max_seats=1, seats_used=0
+UPDATE registration_tokens
+SET seats_used = 0,
+    max_seats = 1
+WHERE status IN ('active', 'expired', 'revoked');
+
+-- Add constraint to ensure seats_used doesn't exceed max_seats
+ALTER TABLE registration_tokens
+    ADD CONSTRAINT chk_seats_used_within_max
+    CHECK (seats_used <= max_seats);
+
+-- Add constraint to ensure positive seat values
+ALTER TABLE registration_tokens
+    ADD CONSTRAINT chk_seats_positive
+    CHECK (max_seats > 0 AND seats_used >= 0);
+
+-- Create table to track all agents that used a token (for audit trail)
+CREATE TABLE IF NOT EXISTS registration_token_usage (
+    id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+    token_id UUID NOT NULL REFERENCES registration_tokens(id) ON DELETE CASCADE,
+    agent_id UUID NOT NULL REFERENCES agents(id) ON DELETE CASCADE,
+    used_at TIMESTAMP DEFAULT NOW(),
+    UNIQUE(token_id, agent_id)
+);
+
+CREATE INDEX idx_token_usage_token_id ON registration_token_usage(token_id);
+CREATE INDEX idx_token_usage_agent_id ON registration_token_usage(agent_id);
+
+-- Backfill token usage table from existing used_by_agent_id
+INSERT INTO registration_token_usage (token_id, agent_id, used_at)
+SELECT id, used_by_agent_id, used_at
+FROM registration_tokens
+WHERE used_by_agent_id IS NOT NULL
+ON CONFLICT (token_id, agent_id) DO NOTHING;
+
+-- Update is_registration_token_valid function to check seats
+CREATE OR REPLACE FUNCTION is_registration_token_valid(token_input VARCHAR)
+RETURNS BOOLEAN AS $$
+DECLARE
+    token_valid BOOLEAN;
+BEGIN
+    SELECT (status = 'active' AND expires_at > NOW() AND seats_used < max_seats) INTO token_valid
+    FROM registration_tokens
+    WHERE token = token_input;
+
+    RETURN COALESCE(token_valid, FALSE);
+END;
+$$ LANGUAGE plpgsql;
+
+-- Update mark_registration_token_used function to increment seats
+CREATE OR REPLACE FUNCTION mark_registration_token_used(token_input VARCHAR, agent_id_param UUID)
+RETURNS BOOLEAN AS $$
+DECLARE
+    rows_updated INTEGER;  -- Fixed: Changed from BOOLEAN to INTEGER to match ROW_COUNT type
+    token_id_val UUID;
+    new_seats_used INT;
+    token_max_seats INT;
+BEGIN
+    -- Get token ID and current seat info
+    SELECT id, seats_used + 1, max_seats INTO token_id_val, new_seats_used, token_max_seats
+    FROM registration_tokens
+    WHERE token = token_input
+      AND status = 'active'
+      AND expires_at > NOW()
+      AND seats_used < max_seats;
+
+    -- If no token found or already full, return false
+    IF token_id_val IS NULL THEN
+        RETURN FALSE;
+    END IF;
+
+    -- Increment seats_used
+    UPDATE registration_tokens
+    SET seats_used = new_seats_used,
+        used_at = CASE
+            WHEN used_at IS NULL THEN NOW()  -- First use
+            ELSE used_at  -- Keep original first use time
+        END,
+        -- Only mark as 'used' if all seats are now taken
+        status = CASE
+            WHEN new_seats_used >= token_max_seats THEN 'used'
+            ELSE 'active'
+        END
+    WHERE token = token_input
+      AND status = 'active';
+
+    GET DIAGNOSTICS rows_updated = ROW_COUNT;
+
+    -- Record this usage in the audit table
+    IF rows_updated > 0 THEN
+        INSERT INTO registration_token_usage (token_id, agent_id, used_at)
+        VALUES (token_id_val, agent_id_param, NOW())
+        ON CONFLICT (token_id, agent_id) DO NOTHING;
+    END IF;
+
+    RETURN rows_updated > 0;
+END;
+$$ LANGUAGE plpgsql;
+
+-- Add comment for documentation
+COMMENT ON COLUMN registration_tokens.max_seats IS 'Maximum number of agents that can register with this token';
+COMMENT ON COLUMN registration_tokens.seats_used IS 'Number of agents that have registered with this token';
+COMMENT ON TABLE registration_token_usage IS 'Audit trail of all agents registered with each token';

aggregator-server/internal/database/migrations/012_create_admin_user.up.sql

@@ -0,0 +1,10 @@
+-- Create admin user from environment configuration
+-- This migration reads the admin credentials from environment variables
+-- and creates the initial admin user in the database
+
+-- Note: This is a placeholder migration that will be executed by the application
+-- The actual user creation logic is handled in the main application startup
+-- to allow for proper password hashing and error handling
+
+-- The admin user creation is handled by the application during startup
+-- This migration file exists for version tracking purposes