chore: implement database crud for AI seat usage (#22681)

Creates a new table `ai_seat_state` to keep track of when users consume an ai_seat. Once a user consumes an AI seat, they will forever in this table (as it stands today).

coderd/database/unique_constraint.go

@@ -7,6 +7,7 @@ type UniqueConstraint string
 // UniqueConstraint enums.
 const (
 	UniqueAgentStatsPkey                                      UniqueConstraint = "agent_stats_pkey"                                                // ALTER TABLE ONLY workspace_agent_stats ADD CONSTRAINT agent_stats_pkey PRIMARY KEY (id);
+	UniqueAiSeatStatePkey                                     UniqueConstraint = "ai_seat_state_pkey"                                              // ALTER TABLE ONLY ai_seat_state ADD CONSTRAINT ai_seat_state_pkey PRIMARY KEY (user_id);
 	UniqueAibridgeInterceptionsPkey                           UniqueConstraint = "aibridge_interceptions_pkey"                                     // ALTER TABLE ONLY aibridge_interceptions ADD CONSTRAINT aibridge_interceptions_pkey PRIMARY KEY (id);
 	UniqueAibridgeTokenUsagesPkey                             UniqueConstraint = "aibridge_token_usages_pkey"                                      // ALTER TABLE ONLY aibridge_token_usages ADD CONSTRAINT aibridge_token_usages_pkey PRIMARY KEY (id);
 	UniqueAibridgeToolUsagesPkey                              UniqueConstraint = "aibridge_tool_usages_pkey"                                       // ALTER TABLE ONLY aibridge_tool_usages ADD CONSTRAINT aibridge_tool_usages_pkey PRIMARY KEY (id);