feat: add hero image focal point picker with anchor positioning (#162)

Add interactive focal point picker for hero images, allowing precise
crop positioning via click or preset buttons (top/center/bottom).
Includes backend validation, migrations, and gallery rendering support.

backend/migrations/core/066_add_hero_anchor_and_category_hero.js

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+/**
+ * Migration: Add hero image anchor position and category-specific hero images
+ *
+ * Issue #162: Add hero_image_anchor column to events table for controlling
+ *             how hero images are cropped (top/center/bottom)
+ *
+ * Issue #163: Add hero_photo_id column to photo_categories table for
+ *             category-specific hero images
+ */
+
+exports.up = async function(knex) {
+  // Add hero_image_anchor to events table (Issue #162)
+  const hasHeroAnchor = await knex.schema.hasColumn('events', 'hero_image_anchor');
+  if (!hasHeroAnchor) {
+    await knex.schema.alterTable('events', function(table) {
+      // Values: 'top', 'center', 'bottom' - defaults to 'center' for backward compatibility
+      table.string('hero_image_anchor', 10).defaultTo('center');
+    });
+    console.log('Added hero_image_anchor column to events table');
+  }
+
+  // Add hero_photo_id to photo_categories table (Issue #163)
+  const hasCategoryHero = await knex.schema.hasColumn('photo_categories', 'hero_photo_id');
+  if (!hasCategoryHero) {
+    await knex.schema.alterTable('photo_categories', function(table) {
+      table.integer('hero_photo_id').references('id').inTable('photos').onDelete('SET NULL');
+    });
+    console.log('Added hero_photo_id column to photo_categories table');
+  }
+};
+
+exports.down = async function(knex) {
+  // Remove hero_image_anchor from events table
+  const hasHeroAnchor = await knex.schema.hasColumn('events', 'hero_image_anchor');
+  if (hasHeroAnchor) {
+    await knex.schema.alterTable('events', function(table) {
+      table.dropColumn('hero_image_anchor');
+    });
+  }
+
+  // Remove hero_photo_id from photo_categories table
+  const hasCategoryHero = await knex.schema.hasColumn('photo_categories', 'hero_photo_id');
+  if (hasCategoryHero) {
+    await knex.schema.alterTable('photo_categories', function(table) {
+      table.dropColumn('hero_photo_id');
+    });
+  }
+};

backend/migrations/core/067_expand_hero_image_anchor.js

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+/**
+ * Migration: Expand hero_image_anchor column to support focal point percentages
+ *
+ * Changes string(10) to string(20) so values like "100% 100%" (9 chars) fit
+ * with room to spare. Existing 'top', 'center', 'bottom' values are preserved.
+ */
+
+exports.up = async function(knex) {
+  const hasColumn = await knex.schema.hasColumn('events', 'hero_image_anchor');
+  if (!hasColumn) {
+    // Column doesn't exist yet – nothing to expand
+    return;
+  }
+
+  // SQLite doesn't truly support ALTER COLUMN, but Knex handles the
+  // rebuild-table strategy internally when we call alterTable.
+  await knex.schema.alterTable('events', function(table) {
+    table.string('hero_image_anchor', 20).defaultTo('center').alter();
+  });
+  console.log('Expanded hero_image_anchor column to string(20)');
+};
+
+exports.down = async function(knex) {
+  const hasColumn = await knex.schema.hasColumn('events', 'hero_image_anchor');
+  if (!hasColumn) {
+    return;
+  }
+
+  await knex.schema.alterTable('events', function(table) {
+    table.string('hero_image_anchor', 10).defaultTo('center').alter();
+  });
+};