chore: add prettier + enforce LF line endings

- Add .prettierrc (double quotes, 2-space, trailing comma es5, LF, 100 cols)
- Add .prettierignore (excludes node_modules, .next, server/, lock files)
- Add .editorconfig (LF + per-language indent rules for all editors)
- Expand .gitattributes to cover all text file types with eol=lf
- Add prettier@^3.5.3 devDep at workspace root with format/format:check scripts
- Add format/format:check scripts to web/package.json

.gitattributes

@@ -1,2 +1,24 @@
+* text=auto eol=lf
+
 *.sh text eol=lf
 *.py text eol=lf
+*.ts text eol=lf
+*.tsx text eol=lf
+*.js text eol=lf
+*.jsx text eol=lf
+*.mjs text eol=lf
+*.cjs text eol=lf
+*.mts text eol=lf
+*.cts text eol=lf
+*.css text eol=lf
+*.html text eol=lf
+*.json text eol=lf
+*.jsonc text eol=lf
+*.yaml text eol=lf
+*.yml text eol=lf
+*.toml text eol=lf
+*.md text eol=lf
+*.mdx text eol=lf
+*.lock text eol=lf
+*.env text eol=lf
+*.env.* text eol=lf