Integrate Copilot with Blink.cmp

- Switch from copilot.vim to zbirenbaum/copilot.lua
- Add blink-cmp-copilot for completion integration
- Configure Blink to show Copilot in completion menu
- Fix plugin import issues

Testing in progress - can be reverted if needed

lua/custom/plugins/blink.lua

@@ -1,6 +1,29 @@
 return {
   'saghen/blink.cmp',
+  dependencies = {
+    "giuxtaposition/blink-cmp-copilot",
+  },
   opts = {
+    sources = {
+      default = { "lsp", "path", "copilot", "buffer" },
+      providers = {
+        copilot = {
+          name = "copilot",
+          module = "blink-cmp-copilot",
+          score_offset = 100, -- High priority to show Copilot near the top
+          async = true,
+        },
+      },
+    },
+    keymap = {
+      preset = 'default',
+      accept = '<C-y>',  -- Your preferred accept key
+    },
+    appearance = {
+      -- Show source of completion (LSP/Copilot/Buffer)
+      use_nvim_cmp_as_default = false,
+      nerd_font_variant = 'mono',
+    },
     fuzzy = {},
   },
 }