docs: remove hardcoded pipeline/batch limits, default to unlimited

Pipeline steps and batch size are now unlimited by default. The old
"20 steps" and "200 images" figures had no basis in the actual code
(MAX_BATCH_SIZE already defaulted to 0/unlimited). Both remain
configurable via MAX_PIPELINE_STEPS and MAX_BATCH_SIZE env vars.

Also includes updated hardware requirements and sidebar nav from
prior documentation audit.

apps/api/src/routes/pipeline.ts

@@ -39,23 +39,23 @@ const pipelineStepSchema = z.object({
 });
 
 /** Schema for a full pipeline definition. */
-const maxSteps = env.MAX_PIPELINE_STEPS > 0 ? env.MAX_PIPELINE_STEPS : 20;
+const stepsSchema =
+  env.MAX_PIPELINE_STEPS > 0
+    ? z
+        .array(pipelineStepSchema)
+        .min(1, "Pipeline must have at least one step")
+        .max(env.MAX_PIPELINE_STEPS, "Pipeline exceeds maximum steps")
+    : z.array(pipelineStepSchema).min(1, "Pipeline must have at least one step");
 
 const pipelineDefinitionSchema = z.object({
-  steps: z
-    .array(pipelineStepSchema)
-    .min(1, "Pipeline must have at least one step")
-    .max(maxSteps, "Pipeline exceeds maximum steps"),
+  steps: stepsSchema,
 });
 
 /** Schema for saving a pipeline. */
 const savePipelineSchema = z.object({
   name: z.string().min(1, "Pipeline name is required").max(100),
   description: z.string().max(500).optional(),
-  steps: z
-    .array(pipelineStepSchema)
-    .min(1, "Pipeline must have at least one step")
-    .max(maxSteps, "Pipeline exceeds maximum steps"),
+  steps: stepsSchema,
 });
 
 export async function registerPipelineRoutes(app: FastifyInstance): Promise<void> {