feat(14-01): add phase_dependencies table to schema

- Add phase_dependencies table mirroring task_dependencies pattern
- Add phaseId and dependsOnPhaseId FK columns with cascade delete
- Add phasesRelations with dependsOn and dependents many relations
- Add phaseDependenciesRelations with phase and dependsOnPhase one relations
- Export PhaseDependency and NewPhaseDependency types

src/db/schema.ts

@@ -60,11 +60,46 @@ export const phasesRelations = relations(phases, ({ one, many }) => ({
     references: [initiatives.id],
   }),
   plans: many(plans),
+  // Dependencies: phases this phase depends on
+  dependsOn: many(phaseDependencies, { relationName: 'dependentPhase' }),
+  // Dependents: phases that depend on this phase
+  dependents: many(phaseDependencies, { relationName: 'dependencyPhase' }),
 }));
 
 export type Phase = InferSelectModel<typeof phases>;
 export type NewPhase = InferInsertModel<typeof phases>;
 
+// ============================================================================
+// PHASE DEPENDENCIES
+// ============================================================================
+
+export const phaseDependencies = sqliteTable('phase_dependencies', {
+  id: text('id').primaryKey(),
+  phaseId: text('phase_id')
+    .notNull()
+    .references(() => phases.id, { onDelete: 'cascade' }),
+  dependsOnPhaseId: text('depends_on_phase_id')
+    .notNull()
+    .references(() => phases.id, { onDelete: 'cascade' }),
+  createdAt: integer('created_at', { mode: 'timestamp' }).notNull(),
+});
+
+export const phaseDependenciesRelations = relations(phaseDependencies, ({ one }) => ({
+  phase: one(phases, {
+    fields: [phaseDependencies.phaseId],
+    references: [phases.id],
+    relationName: 'dependentPhase',
+  }),
+  dependsOnPhase: one(phases, {
+    fields: [phaseDependencies.dependsOnPhaseId],
+    references: [phases.id],
+    relationName: 'dependencyPhase',
+  }),
+}));
+
+export type PhaseDependency = InferSelectModel<typeof phaseDependencies>;
+export type NewPhaseDependency = InferInsertModel<typeof phaseDependencies>;
+
 // ============================================================================
 // PLANS
 // ============================================================================